KVM: PPC: Book3s: PR: Add SPAPR H_BULK_REMOVE support

SPAPR support includes various in-kernel hypercalls, improving performance
by cutting out the exit to userspace.  H_BULK_REMOVE is implemented in this
patch.

Signed-off-by: Matt Evans <matt@ozlabs.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>