powerpc: Work around little endian gcc bug

Temporarily work around an ICE we are seeing while building
in little endian mode:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57134



Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>