RDMA/erdma: Notify the latest PI to FW for reflushing when necessary

RDMA/erdma: Notify the latest PI to FW for reflushing when necessary

Firmware is responsible for flushing WRs in HW, and it's a little
difficult for firmware to get the latest PI of QPs, especially for RQs
after QP state being changed to ERROR. So we introduce a new CMDQ command,
by which driver can notify to latest PI to FW, and then FW can flush all
posted WRs.

Link: https://lore.kernel.org/r/20221116023107.82835-4-chengyou@linux.alibaba.com
Signed-off-by: Cheng Xu <chengyou@linux.alibaba.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>