RDMA/hns: The UD mode can only be configured with DCQCN

Due to hardware limitations, only DCQCN is supported for UD. Therefore, the
default algorithm for UD is set to DCQCN.

Fixes: f91696f2

 ("RDMA/hns: Support congestion control type selection according to the FW")
Signed-off-by: Luoyouming <luoyouming@huawei.com>
Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
Link: https://lore.kernel.org/r/20231017125239.164455-6-huangjunxian6@hisilicon.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>