RDMA/hns: Optimize eqe buffer allocation flow

The eqe has a private multi-hop addressing implementation, but there is
already a set of interfaces in the hns driver that can achieve this.

So, simplify the eqe buffer allocation process by using the mtr interface
and remove large amount of repeated logic.

Link: https://lore.kernel.org/r/20200126145835.11368-1-liweihang@huawei.com


Signed-off-by: Xi Wang <wangxi11@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>