powerpc/boot: Expose Kconfig symbols to wrapper

Currently the wrapper is built without including anything in
$(src)/include/, which means there are no CONFIG_ symbols defined.
This means the platform specific serial drivers were never enabled.

We now copy the definitions into the boot directory, so any C file can
now include autoconf.h to depend on configuration options.

Fixes: 866bfc75f4 ("powerpc: conditionally compile platform-specific serial drivers")
Signed-off-by: Joel Stanley <joel@jms.id.au>
[mpe: Fix to use $(objtree) to find autoconf.h]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/boot/.gitignore

@@ -44,4 +44,5 @@ fdt_sw.c
 fdt_wip.c
 libfdt.h
 libfdt_internal.h
+autoconf.h
 

arch/powerpc/boot/Makefile

@@ -197,9 +197,14 @@ $(obj)/empty.c:
 $(obj)/zImage.coff.lds $(obj)/zImage.ps3.lds : $(obj)/%: $(srctree)/$(src)/%.S
 	$(Q)cp $< $@
 
+$(obj)/serial.c: $(obj)/autoconf.h
+
+$(obj)/autoconf.h: $(obj)/%: $(objtree)/include/generated/%
+	$(Q)cp $< $@
+
 clean-files := $(zlib-) $(zlibheader-) $(zliblinuxheader-) \
 		$(zlib-decomp-) $(libfdt) $(libfdtheader) \
-		empty.c zImage.coff.lds zImage.ps3.lds zImage.lds
+		autoconf.h empty.c zImage.coff.lds zImage.ps3.lds zImage.lds
 
 quiet_cmd_bootcc = BOOTCC  $@
       cmd_bootcc = $(BOOTCC) -Wp,-MD,$(depfile) $(BOOTCFLAGS) -c -o $@ $<

arch/powerpc/boot/serial.c

@@ -18,6 +18,7 @@
 #include "stdio.h"
 #include "io.h"
 #include "ops.h"
+#include "autoconf.h"
 
 static int serial_open(void)
 {