hw/arm: xenpvh: Break out a common PVH machine

Break out a common Xen PVH machine in preparation for
adding a x86 Xen PVH machine.

Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
6 files changed