[PATCH] ppc32: Fix building 32bit kernel for 64bit machines

When building a ppc32 MULTIPLATFORM kernel for a 64bit pmac, we try and
build certain files or use certain functions that make no sense in that
context.  This catches the last of these.

Signed-off-by: Tom Rini <trini@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>