asm-generic/nds32: don't redefine cacheflush primitives

The commit c296d4dc13 ("asm-generic: fix a compilation warning") changed
asm-generic/cachflush.h to use static inlines instead of macros and as a
result the nds32 build with CONFIG_CPU_CACHE_ALIASING=n fails:

  CC      init/main.o
In file included from arch/nds32/include/asm/cacheflush.h:43,
                 from include/linux/highmem.h:12,
                 from include/linux/pagemap.h:11,
                 from include/linux/blkdev.h:16,
                 from include/linux/blk-cgroup.h:23,
                 from include/linux/writeback.h:14,
                 from init/main.c:44:
include/asm-generic/cacheflush.h:50:20: error: static declaration of 'flush_icache_range' follows non-static declaration
 static inline void flush_icache_range(unsigned long start, unsigned long end)
                    ^~~~~~~~~~~~~~~~~~
In file included from include/linux/highmem.h:12,
                 from include/linux/pagemap.h:11,
                 from include/linux/blkdev.h:16,
                 from include/linux/blk-cgroup.h:23,
                 from include/linux/writeback.h:14,
                 from init/main.c:44:
arch/nds32/include/asm/cacheflush.h:11:6: note: previous declaration of 'flush_icache_range' was here
 void flush_icache_range(unsigned long start, unsigned long end);
      ^~~~~~~~~~~~~~~~~~

Surround the inline functions in asm-generic/cacheflush.h by ifdef's so
that architectures could override them and add the required overrides to
nds32.

Fixes: c296d4dc13 ("asm-generic: fix a compilation warning")
Link: https://lore.kernel.org/lkml/201912212139.yptX8CsV%25lkp@intel.com/
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Greentime Hu <green.hu@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/nds32/include/asm/cacheflush.h

@@ -9,7 +9,11 @@
 #define PG_dcache_dirty PG_arch_1
 
 void flush_icache_range(unsigned long start, unsigned long end);
+#define flush_icache_range flush_icache_range
+
 void flush_icache_page(struct vm_area_struct *vma, struct page *page);
+#define flush_icache_page flush_icache_page
+
 #ifdef CONFIG_CPU_CACHE_ALIASING
 void flush_cache_mm(struct mm_struct *mm);
 void flush_cache_dup_mm(struct mm_struct *mm);
@@ -40,12 +44,11 @@ void invalidate_kernel_vmap_range(void *addr, int size);
 #define flush_dcache_mmap_unlock(mapping) xa_unlock_irq(&(mapping)->i_pages)
 
 #else
-#include <asm-generic/cacheflush.h>
-#undef flush_icache_range
-#undef flush_icache_page
-#undef flush_icache_user_range
 void flush_icache_user_range(struct vm_area_struct *vma, struct page *page,
 	                     unsigned long addr, int len);
+#define flush_icache_user_range flush_icache_user_range
+
+#include <asm-generic/cacheflush.h>
 #endif
 
 #endif /* __NDS32_CACHEFLUSH_H__ */

include/asm-generic/cacheflush.h

@@ -11,71 +11,102 @@
  * The cache doesn't need to be flushed when TLB entries change when
  * the cache is mapped to physical memory, not virtual memory
  */
+#ifndef flush_cache_all
 static inline void flush_cache_all(void)
 {
 }
+#endif
 
+#ifndef flush_cache_mm
 static inline void flush_cache_mm(struct mm_struct *mm)
 {
 }
+#endif
 
+#ifndef flush_cache_dup_mm
 static inline void flush_cache_dup_mm(struct mm_struct *mm)
 {
 }
+#endif
 
+#ifndef flush_cache_range
 static inline void flush_cache_range(struct vm_area_struct *vma,
 				     unsigned long start,
 				     unsigned long end)
 {
 }
+#endif
 
+#ifndef flush_cache_page
 static inline void flush_cache_page(struct vm_area_struct *vma,
 				    unsigned long vmaddr,
 				    unsigned long pfn)
 {
 }
+#endif
 
+#ifndef flush_dcache_page
 static inline void flush_dcache_page(struct page *page)
 {
 }
+#endif
 
+#ifndef flush_dcache_mmap_lock
 static inline void flush_dcache_mmap_lock(struct address_space *mapping)
 {
 }
+#endif
 
+#ifndef flush_dcache_mmap_unlock
 static inline void flush_dcache_mmap_unlock(struct address_space *mapping)
 {
 }
+#endif
 
+#ifndef flush_icache_range
 static inline void flush_icache_range(unsigned long start, unsigned long end)
 {
 }
+#endif
 
+#ifndef flush_icache_page
 static inline void flush_icache_page(struct vm_area_struct *vma,
 				     struct page *page)
 {
 }
+#endif
 
+#ifndef flush_icache_user_range
 static inline void flush_icache_user_range(struct vm_area_struct *vma,
 					   struct page *page,
 					   unsigned long addr, int len)
 {
 }
+#endif
 
+#ifndef flush_cache_vmap
 static inline void flush_cache_vmap(unsigned long start, unsigned long end)
 {
 }
+#endif
 
+#ifndef flush_cache_vunmap
 static inline void flush_cache_vunmap(unsigned long start, unsigned long end)
 {
 }
+#endif
 
-#define copy_to_user_page(vma, page, vaddr, dst, src, len) \
+#ifndef copy_to_user_page
+#define copy_to_user_page(vma, page, vaddr, dst, src, len)	\
 	do { \
 		memcpy(dst, src, len); \
 		flush_icache_user_range(vma, page, vaddr, len); \
 	} while (0)
+#endif
+
+#ifndef copy_from_user_page
 #define copy_from_user_page(vma, page, vaddr, dst, src, len) \
 	memcpy(dst, src, len)
+#endif
 
 #endif /* __ASM_CACHEFLUSH_H */