rdma/cxgb4: Fix memory leaks during module exit

Fix memory leaks of iw_cxgb4 module in the exit path

Signed-off-by: Raju Rangoju <rajur@chelsio.com>
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>