iw_cxgb4: remove the stid on listen create failure

If a listen create fails, then the server tid (stid) is incorrectly left
in the stid idr table, which can cause a touch-after-free if the stid
is looked up and the already freed endpoint is touched.  So make sure
and remove it in the error path.

Cc: stable@vger.kernel.org
Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>