powerpc/compat: 32-bit little endian machine name is ppcle, not ppc

I noticed this when testing setarch. No, we don't magically
support a big endian userspace on a little endian kernel.

Signed-off-by: Anton Blanchard <anton@samba.org>
Cc: stable@vger.kernel.org # v3.10+
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>