RDMA/hns: Correct the value of HNS_ROCE_HEM_CHUNK_LEN

RDMA/hns: Correct the value of HNS_ROCE_HEM_CHUNK_LEN

[ Upstream commit 531eb45b3da4267fc2a64233ba256c8ffb02edd2 ]

Size of pointer to buf field of struct hns_roce_hem_chunk should be
considered when calculating HNS_ROCE_HEM_CHUNK_LEN, or sg table size will
be larger than expected when allocating hem.

Fixes: 9a4435375cd1 ("IB/hns: Add driver files for hns RoCE driver")
Link: https://lore.kernel.org/r/1572575610-52530-2-git-send-email-liweihang@hisilicon.com
Signed-off-by: Sirong Wang <wangsirong@huawei.com>
Signed-off-by: Weihang Li <liweihang@hisilicon.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>