RDMA/hns: Response dmac to userspace

While creating AH, dmac is already resolved in kernel. Response dmac
to userspace so that userspace doesn't need to resolve dmac repeatedly.

Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
Link: https://lore.kernel.org/r/20231207114231.2872104-3-huangjunxian6@hisilicon.com


Signed-off-by: Leon Romanovsky <leon@kernel.org>