KVM: PPC: bookehv: remove SET_VCPU

The SET_VCPU macro is a leftover from times when the vcpu struct wasn't
stored in the thread on vcpu_load/put. It's not needed anymore. Remove it.

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