[media] ivtv: improve subscribe_event handling

Simplify logic and call v4l2_ctrl_subscribe_event() directly instead
of copying its content over to ivtv_subscribe_event().

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/pci/ivtv/ivtv-ioctl.c

@@ -1506,10 +1506,8 @@ static int ivtv_subscribe_event(struct v4l2_fh *fh, const struct v4l2_event_subs
 	case V4L2_EVENT_VSYNC:
 	case V4L2_EVENT_EOS:
 		return v4l2_event_subscribe(fh, sub, 0, NULL);
-	case V4L2_EVENT_CTRL:
-		return v4l2_event_subscribe(fh, sub, 0, &v4l2_ctrl_sub_ev_ops);
 	default:
-		return -EINVAL;
+		return v4l2_ctrl_subscribe_event(fh, sub);
 	}
 }