[SCSI] cxgbi3: remove unnecessary NULL test

Stanse found that c3cn is poked many times around in
cxgb3i_conn_pdu_ready, there is no need to check if it is NULL.

Remove the test.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Acked-by: Karen Xie <kxie@chelsio.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>