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

drivers/scsi/pm8001/pm8001_sas.c: In function 'pm8001_I_T_nexus_event_handler':
drivers/scsi/pm8001/pm8001_sas.c:1052:6: warning:
 variable 'device_id' set but not used [-Wunused-but-set-variable]

drivers/scsi/pm8001/pm8001_sas.c: In function 'pm8001_abort_task':
drivers/scsi/pm8001/pm8001_sas.c:1191:6: warning:
 variable 'device_id' set but not used [-Wunused-but-set-variable]
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Jack Wang <jinpu.wang@profitbricks.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>