RDMA/hns: Add enable judgement for UD vlan

According to the hardware modification, the vlan of the UD packet is based
on the ud_vlan_en field of the UD wqe to determine whether to add a vlan
header to the UD packet. The ud_vlan_en field is filled by the driver
according to the net device.

Signed-off-by: Lijun Ou <oulijun@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>