RDMA/cxgb4: Fix possible memory leak in RX_PKT processing

If cxgb4_ofld_send() returns < 0, then send_fw_pass_open_req() must
free the request skb and the saved skb with the tcp header.

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