KVM: s390: VSIE: sort out virtual/physical address in pin_guest_page

pin_guest_page() used page_to_virt() to calculate the hpa of the pinned
page. This currently works, because virtual and physical addresses are
the same. Use page_to_phys() instead to resolve the virtual-real address
confusion.

One caller of pin_guest_page() actually expected the hpa to be a hva, so
add the missing phys_to_virt() conversion here.

Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Link: https://lore.kernel.org/r/20221025082039.117372-2-nrb@linux.ibm.com
Message-Id: <20221025082039.117372-2-nrb@linux.ibm.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>