RDMA/hns: Support configuring POE channels and creating POE CQs

driver inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8C2IP



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This patch provides a pair of APIs rdma_register_poe_channel()/
rdma_unregister_poe_channel() to support register/unregister POE
channels which could be used for CQs.

At the same time, this patch also supports user creation of CQ bound
to a POE channel.

BTW, This patch also add a debugfs for POE to help with problem
diagnosis.

Signed-off-by: Chengchang Tang <tangchengchang@huawei.com>