RDMA/hns: Remove unused CMDQ member

The hcr_mutex was used to serialize mailbox post. Now that mailbox
supports concurrency, this variable is no longer useful.

Fixes: a389d016 ("RDMA/hns: Enable all CMDQ context")
Link: https://lore.kernel.org/r/1621482876-35780-4-git-send-email-liweihang@huawei.com


Signed-off-by: Lang Cheng <chenglang@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>