powerpc: Emulate instructions in little endian mode

Alistair noticed we got a SIGILL on userspace mfpvr instructions.

Remove the little endian check in the emulation code, it is
probably there to protect against the old pseudo little endian
implementations but doesn't make sense for real little endian.

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