KVM: s390: unintended fallthrough for external call

We must not fallthrough if the conditions for external call are not met.
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: NThomas Huth <thuth@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org

arch/s390/kvm/interrupt.c

@@ -86,6 +86,7 @@ static int __must_check __interrupt_is_deliverable(struct kvm_vcpu *vcpu,
 			return 0;
 		if (vcpu->arch.sie_block->gcr[0] & 0x2000ul)
 			return 1;
+		return 0;
 	case KVM_S390_INT_EMERGENCY:
 		if (psw_extint_disabled(vcpu))
 			return 0;