scsi: hisi_sas: Remove set but not used variable 'dq_list'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/scsi/hisi_sas/hisi_sas_v1_hw.c: In function 'start_delivery_v1_hw':
drivers/scsi/hisi_sas/hisi_sas_v1_hw.c:907:20: warning:
 variable 'dq_list' set but not used [-Wunused-but-set-variable]

drivers/scsi/hisi_sas/hisi_sas_v2_hw.c: In function 'start_delivery_v2_hw':
drivers/scsi/hisi_sas/hisi_sas_v2_hw.c:1671:20: warning:
 variable 'dq_list' set but not used [-Wunused-but-set-variable]

drivers/scsi/hisi_sas/hisi_sas_v3_hw.c: In function 'start_delivery_v3_hw':
drivers/scsi/hisi_sas/hisi_sas_v3_hw.c:889:20: warning:
 variable 'dq_list' set but not used [-Wunused-but-set-variable]

It never used since introduction in commit
fa222db0

 ("scsi: hisi_sas: Don't lock DQ for complete task sending")

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>