RDMA/cxgb3: Silently ignore close reply after abort.

Remove bad BUG_ON() that can trigger in correct operation from
close_con_rpl().  It is possible to get a close_rpl message on a dead
connection.  The sequence is:

	- host refs ep for close exchange
	- host posts close_req
	- hw posts PEER_ABORT from incoming RST
	- host marks ep DEAD
	- host posts ABORT_RPL and releases ep resources
	- hw posts CLOSE_RPL
	- host derefs ep and ep freed.

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