RDMA/hns: Fix GMV table pagesize

GMV's BA table only supports 4K pages. Currently, PAGESIZE is used to
calculate gmv_bt_num, which will cause an abnormal number of gmv_bt_num
in a 64K OS.

Fixes: d6d91e46

 ("RDMA/hns: Add support for configuring GMV table")
Signed-off-by: Chengchang Tang <tangchengchang@huawei.com>
Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
Link: https://lore.kernel.org/r/20240412091616.370789-8-huangjunxian6@hisilicon.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>