RDMA/cxgb3: Handle NULL inetdev pointer in iwch_query_port()

in_dev_get() can return NULL.  If it does, iwch_query_port() will crash.
Handle the NULL case by mapping it to port state INIT.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>