RDMA/hns: Support getting xrcd num from firmware

driver inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I6WAZI



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Support driver gets the num_xrcds and reserved_xrcds from firmware.

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