scsi: cxgb4i: fix Tx skb leak

In case of connection reset Tx skb queue can have some skbs which are
not transmitted so purge Tx skb queue in release_offload_resources() to
avoid skb leak.

Signed-off-by: Varun Prakash <varun@chelsio.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>