mlx4_en: Assign dummy event handler for TX queue

The low level driver always assumes this handler exists.
The lack of it could cause kernel panic

Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/mlx4/en_resources.c

@@ -94,3 +94,9 @@ void mlx4_en_unmap_buffer(struct mlx4_buf *buf)
 
 	vunmap(buf->direct.buf);
 }
+
+void mlx4_en_sqp_event(struct mlx4_qp *qp, enum mlx4_event event)
+{
+    return;
+}
+