iw_cxgb4: gracefully handle unknown CQE status errors

c4iw_poll_cq_on() shouldn't fail the poll operation just because
the CQE status is unknown.  Rather, it should map this to the
"fatal error" status and log the anomaly.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>