s390/cio: Set vfio-ccw FSM state before ioeventfd

Otherwise, the guest can believe it's okay to start another I/O
and bump into the non-idle state.  This results in a cc=2 (with
the asynchronous CSCH/HSCH code) returned to the guest, which is
unfortunate since everything is otherwise working normally.
Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Message-Id: <20190514234248.36203-3-farman@linux.ibm.com>
Reviewed-by: Farhan Ali <alifm@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

drivers/s390/cio/vfio_ccw_drv.c

@@ -95,11 +95,11 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work)
 	memcpy(private->io_region->irb_area, irb, sizeof(*irb));
 	mutex_unlock(&private->io_mutex);
 
-	if (private->io_trigger)
-		eventfd_signal(private->io_trigger, 1);
-
 	if (private->mdev && is_final)
 		private->state = VFIO_CCW_STATE_IDLE;
+
+	if (private->io_trigger)
+		eventfd_signal(private->io_trigger, 1);
 }
 
 /*