[SCSI] iscsi_tcp: Remove unused field iscsi_conn from struct iscsi_sw_tcp_conn

iscsi_conn is not used so remove it from iscsi_sw_tcp_conn.

Signed-off-by: Avi Kaplan <savik751@gmail.com>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>