KVM: PPC: Add fields to shadow vcpu

After a lot of thought on how to make the entry / exit code easier,
I figured it'd be clever to put even more register state into the
shadow vcpu. That way we have more registers available to use, making
the code easier to read.

So this patch adds a few new fields to that shadow vcpu. Later on we
will remove the originals from the vcpu and paca.

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