caif_virtio: Use vringh_notify_enable correctly

Check on the correct return value from
vringh_notify_enable_kern(). It returns false if
more packets are available, not true.

Signed-off-by: Sjur Brændeland <sjur.brandeland@stericsson.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/net/caif/caif_virtio.c

@@ -318,7 +318,7 @@ static int cfv_rx_poll(struct napi_struct *napi, int quota)
 
 		/* Really out of patckets? (stolen from virtio_net)*/
 		napi_complete(napi);
-		if (unlikely(vringh_notify_enable_kern(cfv->vr_rx)) &&
+		if (unlikely(!vringh_notify_enable_kern(cfv->vr_rx)) &&
 		    napi_schedule_prep(napi)) {
 			vringh_notify_disable_kern(cfv->vr_rx);
 			__napi_schedule(napi);