net/mlx5: fix drop queue creation error

Creating a drop queue in mlx5 ends by creating a non polled queue, but if
the associated work queue could not be created the error was not handled
ending in a undefined situation.

Fixes: 2097d0d1e2 ("net/mlx5: support basic flow items and actions")
Cc: stable@dpdk.org

Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>

drivers/net/mlx5/mlx5_flow.c

@@ -902,6 +902,12 @@ priv_flow_create_action_queue(struct priv *priv,
 						 .pd = priv->pd,
 						 .cq = rte_flow->cq,
 						 });
+		if (!rte_flow->wq) {
+			rte_flow_error_set(error, ENOMEM,
+					   RTE_FLOW_ERROR_TYPE_HANDLE,
+					   NULL, "cannot allocate WQ");
+			goto error;
+		}
 	} else {
 		rxq = container_of((*priv->rxqs)[action->queue_id],
 				   struct rxq_ctrl, rxq);