KVM: s390: enable Transactional Execution

This patch enables transactional execution for KVM guests
on s390 systems zec12 or later.

We rework the allocation of the page containing the sie_block
to also back the Interception Transaction Diagnostic Block.
If available the TE facilities will be enabled.

Setting bit 73 and 50 in vfacilities bitmask reveals the HW
facilities Transactional Memory and Constraint Transactional
Memory respectively to the KVM guest.

Furthermore, the patch restores the Program-Interruption TDB
from the Interception TDB in case a program interception has
occurred and the ITDB has a valid format.

Signed-off-by: Michael Mueller <mimu@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>