s390/pci: stash associated GISA designation

s390/pci: stash associated GISA designation

For passthrough devices, we will need to know the GISA designation of the
guest if interpretation facilities are to be used.  Setup to stash this in
the zdev and set a default of 0 (no GISA designation) for now; a subsequent
patch will set a valid GISA designation for passthrough devices.
Also, extend mpcific routines to specify this stashed designation as part
of the mpcific command.

Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Link: https://lore.kernel.org/r/20220606203325.110625-9-mjrosato@linux.ibm.com
Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>