KVM: s390: vsie: fix < 8k check for the itdba

By missing an "L", we might detect some addresses to be <8k,
although they are not.

e.g. for itdba = 100001fff
!(gpa & ~0x1fffU) -> 1
!(gpa & ~0x1fffUL) -> 0

So we would report a SIE validity intercept although everything is fine.

Fixes: 166ecb3d ("KVM: s390: vsie: support transactional execution")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Cc: stable@vger.kernel.org # v4.8+
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>