RDMA/hns: Fix the bug while use multi-hop of pbl

[ Upstream commit 4af07f01f7a787ba5158352b98c9e3cb74995a1c ]

It will prevent multiply overflow when defines the pbl for u64 type.

Signed-off-by: Lijun Ou <oulijun@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>