memory: don't hand MFN info to translated guests

memory: don't hand MFN info to translated guests

We shouldn't hand MFN info back from increase-reservation for
translated domains, just like we don't for populate-physmap and
memory-exchange. For full symmetry also check for a NULL guest handle
in populate_physmap() (but note this makes no sense in
memory_exchange(), as there the array is also an input).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Released-acked-by: Julien Grall <julien.grall@arm.com>