PPC: Enable hint bits for lwarx/ldarx

PPC: Enable hint bits for lwarx/ldarx

The lwarx and ldarx instructions have a bit to give some hint to the
CPU which is safe to ignore. We currently refuse to accept any instruction
with that bit set, as it used to be declared MBZ.

Let's remove the reserved bit and make the instruction work as expected.
This fixes Linux boot for ppc64.

Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Andreas Färber <andreas.faerber@web.de>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>