passthrough: rework hwdom_pvh_reqs to use it also on ARM

passthrough: rework hwdom_pvh_reqs to use it also on ARM

Hardware domain on ARM will have the same requirements as hwdom PVH when iommu
is enabled. Both PVH and ARM guest has paging mode translate enabled, so Xen
can use it to know if it needs to check the requirements.

Rename the function and remove "pvh" word in the panic message.

Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>