mn10300: only add -mmem-funcs to KBUILD_CFLAGS if gcc supports it

commit 9957423f upstream.

It seems the current (gcc 4.6.3) no longer provides this so make it
conditional.

As reported by Tony before, the mn10300 architecture cross-compiles with
gcc-4.6.3 if -mmem-funcs is not added to KBUILD_CFLAGS.
Reported-by: Tony Breeds <tony@bakeyournoodle.com>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Koichi Yasutake <yasutake.koichi@jp.panasonic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

arch/mn10300/Makefile

@@ -26,7 +26,7 @@ CHECKFLAGS	+=
 PROCESSOR	:= unset
 UNIT		:= unset
 
-KBUILD_CFLAGS	+= -mam33 -mmem-funcs -DCPU=AM33
+KBUILD_CFLAGS	+= -mam33 -DCPU=AM33 $(call cc-option,-mmem-funcs,)
 KBUILD_AFLAGS	+= -mam33 -DCPU=AM33
 
 ifeq ($(CONFIG_MN10300_CURRENT_IN_E2),y)