fs: cbfs: Fix build of fs/cbfs/cbfs.c when building u-boot sandbox on x86 32-bit

fs: cbfs: Fix build of fs/cbfs/cbfs.c when building u-boot sandbox on x86 32-bit

Fix the following build errors when building sandbox on x86 32-bit:

	In file included from fs/cbfs/cbfs.c:8:0:
	include/malloc.h:364:7: error: conflicting types for 'memset'
	void* memset(void*, int, size_t);
	^
	In file included from include/compiler.h:123:0,
			from include/cbfs.h:10,
			from fs/cbfs/cbfs.c:7:
	include/linux/string.h:78:15: note: previous declaration of 'memset' was here
	extern void * memset(void *,int,__kernel_size_t);
		^
	In file included from fs/cbfs/cbfs.c:8:0:
	include/malloc.h:365:7: error: conflicting types for 'memcpy'
	void* memcpy(void*, const void*, size_t);
	^
	In file included from include/compiler.h:123:0,
			from include/cbfs.h:10,
			from fs/cbfs/cbfs.c:7:
	include/linux/string.h:81:15: note: previous declaration of 'memcpy' was here
	extern void * memcpy(void *,const void *,__kernel_size_t);
		^
	scripts/Makefile.build:280: recipe for target 'fs/cbfs/cbfs.o' failed

Signed-off-by: Guillaume GARDET <guillaume.gardet@free.fr>
Cc: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>