Currently, WQE and EQE table have already used the mtr interface to config
and access memory by multi-hop addressing when hopnum is from 1 to 3. But
if hopnum is 0, each table need write its own but repetitive logic, and
many duplicate code exists in the mtr interfaces invoke process.

So wraps the public logic as 3 functions: hns_roce_mtr_create(),
hns_roce_mtr_destroy() and hns_roce_mtr_map() to support hopnum ranges from
0 to 3. In addition, makes the mtr interfaces easier to use.

Link: https://lore.kernel.org/r/1586779091-51410-2-git-send-email-liweihang@huawei.comSigned-off-by: Xi Wang <wangxi11@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>