RDMA/hns: Fix PBL page MTR find

Now, The address of the first two pages in the MR will be searched, which
use to speed up the lookup of the pbl table for hardware.  An exception
will occur when there is only one page in this MR.  This patch fix the
number of page to search.

Fixes: 9b2cf76c ("RDMA/hns: Optimize PBL buffer allocation process")
Link: https://lore.kernel.org/r/20221126102911.2921820-4-xuhaoyue1@hisilicon.com


Signed-off-by: Chengchang Tang <tangchengchang@huawei.com>
Signed-off-by: Haoyue Xu <xuhaoyue1@hisilicon.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>