KVM: s390: preserve deliverable_mask in __airqs_kick_single_vcpu

KVM: s390: preserve deliverable_mask in __airqs_kick_single_vcpu

Changing the deliverable mask in __airqs_kick_single_vcpu() is a bug. If
one idle vcpu can't take the interrupts we want to deliver, we should
look for another vcpu that can, instead of saying that we don't want
to deliver these interrupts by clearing the bits from the
deliverable_mask.

Fixes: a2ab0f7e961a ("KVM: s390: add gib_alert_irq_handler()")
Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Michael Mueller <mimu@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Link: https://lore.kernel.org/r/20211019175401.3757927-3-pasic@linux.ibm.com
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>