RDMA/hns: Remove some magic numbers

Use macros instead of magic numbers to represent shift of dma_handle_wqe,
dma_handle_idx and UDP destination port number of RoCEv2.

Link: https://lore.kernel.org/r/1612517974-31867-10-git-send-email-liweihang@huawei.com


Signed-off-by: Xinhao Liu <liuxinhao5@hisilicon.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>