IB/hns: Implement the add_gid/del_gid and optimize the GIDs management

IB core has implemented the calculation of GIDs and the management
of GID tables, and it is now responsible to supply query function
for GIDs. So the calculation of GIDs and the management of GID
tables in the RoCE driver is redundant.

The patch is to implement the add_gid/del_gid to set the GIDs in
the RoCE driver, remove the redundant calculation and management of
GIDs in the notifier call of the net device and the inet, and
update the query_gid.

Signed-off-by: Shaobo Xu <xushaobo2@huawei.com>
Reviewed-by: Wei Hu (Xavier) <xavier.huwei@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>