KVM: fix error handling for out of range irq

find_index_from_host_irq returns 0 on error
but callers assume < 0 on error. This should
not matter much: an out of range irq should never happen since
irq handler was registered with this irq #,
and even if it does we get a spurious msix irq in guest
and typically nothing terrible happens.

Still, better to make it consistent.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

virt/kvm/assigned-dev.c

@@ -49,10 +49,8 @@ static int find_index_from_host_irq(struct kvm_assigned_dev_kernel
 			index = i;
 			break;
 		}
-	if (index < 0) {
+	if (index < 0)
 		printk(KERN_WARNING "Fail to find correlated MSI-X entry!\n");
-		return 0;
-	}
 
 	return index;
 }