RDMA/ionic: Fix potential NULL pointer dereference in ionic_query_port

In the Linux kernel, the following vulnerability has been resolved:

RDMA/ionic: Fix potential NULL pointer dereference in ionic_query_port

The function ionic_query_port() calls ib_device_get_netdev() without

checking the return value which could lead to NULL pointer dereference,

Fix it by checking the return value and return -ENODEV if the 'ndev' is

NULL.