uaccess: remove CONFIG_SET_FS

There are no remaining callers of set_fs(), so CONFIG_SET_FS
can be removed globally, along with the thread_info field and
any references to it.

This turns access_ok() into a cheaper check against TASK_SIZE_MAX.

As CONFIG_SET_FS is now gone, drop all remaining references to
set_fs()/get_fs(), mm_segment_t, user_addr_max() and uaccess_kernel().

Acked-by: Sam Ravnborg <sam@ravnborg.org> # for sparc32 changes
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Tested-by: Sergey Matyukevich <sergey.matyukevich@synopsys.com> # for arc changes
Acked-by: Stafford Horne <shorne@gmail.com> # [openrisc, asm-generic]
Acked-by: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

mm/memory.c

@@ -5256,14 +5256,6 @@ void print_vma_addr(char *prefix, unsigned long ip)
 #if defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP)
 void __might_fault(const char *file, int line)
 {
-	/*
-	 * Some code (nfs/sunrpc) uses socket ops on kernel memory while
-	 * holding the mmap_lock, this is safe because kernel memory doesn't
-	 * get paged out, therefore we'll never actually fault, and the
-	 * below annotations will generate false positives.
-	 */
-	if (uaccess_kernel())
-		return;
 	if (pagefault_disabled())
 		return;
 	__might_sleep(file, line);