xen: don't use xenstore to save/restore physmap anymore

xen: don't use xenstore to save/restore physmap anymore

If we have a system with xenforeignmemory_map2() implemented
we don't need to save/restore physmap on suspend/restore
anymore. In case we resume a VM without physmap - try to
recreate the physmap during memory region restore phase and
remap map cache entries accordingly. The old code is left
for compatibility reasons.

Signed-off-by: Igor Druzhinin <[email protected]>
Reviewed-by: Paul Durrant <[email protected]>
Reviewed-by: Stefano Stabellini <[email protected]>
Signed-off-by: Stefano Stabellini <[email protected]>