KVM: s390: remove kvm_s390_ from gisa static inline functions

This will shorten the length of code lines. All GISA related
static inline functions are local to interrupt.c.

Signed-off-by: Michael Mueller <mimu@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Message-Id: <20190131085247.13826-7-mimu@linux.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>