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

driver inclusion
category: bugfix
bugzilla: 50786

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The base address table is allocated by dma allocator, and the size is
always aligned to PAGE_SIZE. If use the fixed size to allocated the table,
the base address entries which stored in table will be smaller than the
actual memory space can store.

Signed-off-by: Xi Wang <wangxi11@huawei.com>
Reviewed-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>