scsi: hisi_sas: Add device attribute experimental_iopoll_q_cnt for v3 hw

Add device attribute experimental_iopoll_q_cnt to indicate how many iopoll
queues are used for v3 hw.

Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
Link: https://lore.kernel.org/r/1678169355-76215-5-git-send-email-chenxiang66@hisilicon.com


Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>