scsi: qla2xxx: Move sess cmd list/lock to driver

Except for debug output in the shutdown path, tcm_qla2xxx is the only
driver using the se_session sess_cmd_list. Move the list to that driver to
facilitate removing the sess_cmd_lock from the main I/O path for the rest
of the drivers.

Link: https://lore.kernel.org/r/1604257174-4524-6-git-send-email-michael.christie@oracle.com
Cc: Nilesh Javali <njavali@marvell.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>