RDMA/hns: Add method for attaching WQE buffer

driver inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I63KVU



----------------------------------------------------------

If a uQP works as DCA mode, the userspace driver need config the WQE buffer
by calling the 'HNS_IB_METHOD_DCA_MEM_ATTACH' method before filling the
WQE. This method will allocate a group of pages from DCA memory pool and
write the configuration of addressing to QPC.

Signed-off-by: Chengchang Tang <tangchengchang@huawei.com>
Reviewed-by: Yangyang Li <liyangyang20@huawei.com>
Reviewed-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>