RDMA/hns: Optimize the base address table config for MTR

RDMA/hns: Optimize the base address table config for MTR

The base address table is allocated by dma allocator, and the size is
always aligned to PAGE_SIZE. If a fixed size is used to allocate the
table, the number of base address entries stored in the table will be
smaller than that can actually stored.

Link: https://lore.kernel.org/r/1621589395-2435-2-git-send-email-liweihang@huawei.com
Signed-off-by: Xi Wang <wangxi11@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>