[media] em28xx: Fix IR unregister logic

The input stop() callback already calls the em28xx_ir_stop method.
Calling it again causes an oops.
Acked-by: NJarod Wilson <jarod@redhat.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/em28xx/em28xx-input.c

@@ -463,11 +463,11 @@ int em28xx_ir_fini(struct em28xx *dev)
 	if (!ir)
 		return 0;
 
-	em28xx_ir_stop(ir->rc);
-	rc_unregister_device(ir->rc);
-	kfree(ir);
+	if (ir->rc)
+		rc_unregister_device(ir->rc);
 
 	/* done */
+	kfree(ir);
 	dev->ir = NULL;
 	return 0;
 }