RDMA/hns: Remove redundant 'num_mtt_segs' and 'max_extend_sg'

The num_mtt_segs and max_extend_sg used to be used for HIP06,
remove them since the HIP06 code has been removed.

Link: https://lore.kernel.org/r/20220922123315.3732205-9-xuhaoyue1@hisilicon.com


Signed-off-by: Yangyang Li <liyangyang20@huawei.com>
Signed-off-by: Haoyue Xu <xuhaoyue1@hisilicon.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>