[PATCH] powerpc32: Set cpu explicitly in kernel compiles

Compile the 32bit kernel with -mcpu=powerpc. This reduces the imagesize
when a compiler is used that defaults to -mtune=power4. It inserts lots
of nops to please the 64bit cpu instruction scheduling. But all these nops
are not needed for 32bit kernels.

Example with SLES10 gcc 4.1.0 and arch/powerpc/configs/pmac32_defconfig:

                    vmlinux  vmlinux.strip  vmlinux.gz
 -O2                4980515     4187528      1846829
 -Os                4618801     3827084      1673333
 -O2 -mcpu=powerpc  4738851     3945868      1816253
 -Os -mcpu=powerpc  4532785     3741068      1664688
Signed-off-by: Olaf Hering <olh@suse.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/Makefile

@@ -104,6 +104,10 @@ ifndef CONFIG_FSL_BOOKE
 CFLAGS		+= -mstring
 endif
 
+ifeq ($(CONFIG_6xx),y)
+CFLAGS		+= -mcpu=powerpc
+endif
+
 cpu-as-$(CONFIG_PPC64BRIDGE)	+= -Wa,-mppc64bridge
 cpu-as-$(CONFIG_4xx)		+= -Wa,-m405
 cpu-as-$(CONFIG_6xx)		+= -Wa,-maltivec