s390/kvm: Mask extra bits from program interrupt code

s390/kvm: Mask extra bits from program interrupt code

The program interrupt code has some extra bits that are sometimes set
by hardware for various reasons; those bits should be ignored when the
program interrupt number is needed for interrupt handling.

Fixes: 05066cafa925 ("s390/mm/fault: Handle guest-related program interrupts in KVM")
Reported-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Tested-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Link: https://lore.kernel.org/r/20241031120316.25462-1-imbrenda@linux.ibm.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>