Add the Interruption Alert Mask (IAM) to the architecture specific
kvm struct. This mask in the GISA is used to define for which ISC
a GIB alert will be issued.

The functions kvm_s390_gisc_register() and kvm_s390_gisc_unregister()
are used to (un)register a GISC (guest ISC) with a virtual machine and
its GISA.

Upon successful completion, kvm_s390_gisc_register() returns the
ISC to be used for GIB alert interruptions. A negative return code
indicates an error during registration.

Theses functions will be used by other adapter types like AP and PCI to
request pass-through interruption support.
Signed-off-by: NMichael Mueller <mimu@linux.ibm.com>
Acked-by: NPierre Morel <pmorel@linux.ibm.com>
Acked-by: NHalil Pasic <pasic@linux.ibm.com>
Reviewed-by: NCornelia Huck <cohuck@redhat.com>
Message-Id: <20190131085247.13826-12-mimu@linux.ibm.com>
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>