net/mlx5: fix configuration without Rx queue

None Rx queue configured in a DPDK application should be supported.
In this mode, the NIC can be used to generate packets without
receiving any ingress traffic.

In the current implementation, once there is no Rx queue specified,
the array to store the queues' pointers is NULL after allocation.
Then the checking of the array allocation prevents the application
from starting up.

By adding another condition checking of the Rx queue number, the
application with none Rx queue can start up successfully.

Fixes: 4cda06c3c35e ("net/mlx5: split Rx queue into shareable and private")
Cc: stable@dpdk.org

Signed-off-by: Bing Zhao <bingz@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>

drivers/net/mlx5/mlx5_ethdev.c

@@ -111,7 +111,7 @@ mlx5_dev_configure(struct rte_eth_dev *dev)
 				       MLX5_MEM_RTE | MLX5_MEM_ZERO,
 				       sizeof(void *) * rxqs_n, 0,
 				       SOCKET_ID_ANY);
-	if (priv->rxq_privs == NULL) {
+	if (rxqs_n && priv->rxq_privs == NULL) {
 		DRV_LOG(ERR, "port %u cannot allocate rxq private data",
 			dev->data->port_id);
 		rte_errno = ENOMEM;