KVM: s390: fix bug in interrupt parameter check

When we convert interrupt data from struct kvm_s390_interrupt to
struct kvm_s390_irq we need to check the data in the input parameter
not the output parameter.

Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>