A native powerpc64-linux gcc can not compile a ppc32 kernel properly.  This
patch fixes it.  It was copied from ppc64.  The change to vmlinux.lds.S
fixes this error:

ld: warning: powerpc:common architecture of input file `init/built-in.o' is
incompatible with powerpc:common64 output
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>