KVM: s390: expose no-DAT to guest and migration support

KVM: s390: expose no-DAT to guest and migration support

The STFLE bit 147 indicates whether the ESSA no-DAT operation code is
valid, the bit is not normally provided to the host; the host is
instead provided with an SCLP bit that indicates whether guests can
support the feature.

This patch:
* enables the STFLE bit in the guest if the corresponding SCLP bit is
  present in the host.
* adds support for migrating the no-DAT bit in the PGSTEs
* fixes the software interpretation of the ESSA instruction that is
  used when migrating, both for the new operation code and for the old
  "set stable", as per specifications.

Signed-off-by: Claudio Imbrenda <[email protected]>
Reviewed-by: Christian Borntraeger <[email protected]>
Acked-by: Cornelia Huck <[email protected]>
Signed-off-by: Christian Borntraeger <[email protected]>