After the "ppc64 monster cleanup," I get

    powerpc-750-linux-gnu-strip: vmlinux: File format not recognized

from my ppc32 strip command when cross-compiling a ppc64 kernel, since
vmlinux is a 64-bit ELF file.  This patch fixes my build (and the
resulting kernel boots fine).
Signed-off-by: Roland Dreier <roland@topspin.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>