KVM: PPC: Implement emulation for lbzux and lhax

We get MMIOs with the weirdest instructions. But every time we do,
we need to improve our emulator to implement them.

So let's do that - this time it's lbzux and lhax's round.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>