RDMA/hns: Refactor extend link table allocation

The timeout link table works in HIP08 ES version and the hns driver only
support the CS version for HIP08, so delete the related code. Then
simplify the buffer allocation for link table to make the code more
readable.

Link: https://lore.kernel.org/r/1621481751-27375-1-git-send-email-liweihang@huawei.com


Signed-off-by: Xi Wang <wangxi11@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>