[POWERPC] Stop the TOC overflowing for large builds

We were using -mno-minimal-toc on everything in arch/powerpc/kernel,
which means that all the functions in there were putting all their
TOC entries in the top-level TOC, and it was overflowing on an
allyesconfig build.  For various reasons, prom_init.c does need
-mno-minimal-toc, but the other .c files in there can use sub-TOCs
quite happily.  This change is sufficient for now to stop the TOC
overflowing; other directories under arch/powerpc also use
-mno-minimal-toc and could also be changed later if necessary.

Lmbench runs with and without this patch showed no significant speed
differences.
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/Makefile

@@ -3,7 +3,7 @@
 #
 
 ifeq ($(CONFIG_PPC64),y)
-EXTRA_CFLAGS	+= -mno-minimal-toc
+CFLAGS_prom_init.o	+= -mno-minimal-toc
 endif
 ifeq ($(CONFIG_PPC32),y)
 CFLAGS_prom_init.o      += -fPIC