scsi: qla2xxx: Remove unused argument from qlt_schedule_sess_for_deletion()

Immeadiate flag is not used for scheduling session deletion.
Remove it to simplfy session deletion code path.

Signed-off-by: Quinn Tran <quinn.tran@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>