scsi: qla2xxx: Fix smatch warning in qla25xx_delete_{rsp|req}_que

This patch fixes following warnings reported by smatch:

drivers/scsi/qla2xxx/qla_mid.c:586 qla25xx_delete_req_que()
error: we previously assumed 'req' could be null (see line 580)

drivers/scsi/qla2xxx/qla_mid.c:602 qla25xx_delete_rsp_que()
error: we previously assumed 'rsp' could be null (see line 596)

Fixes: 7867b98d ("scsi: qla2xxx: Fix memory leak in dual/target mode")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>