RDMA/hns: Remove redundant 'bt_level' for hem_list_alloc_item()

The 'bt_level' parameter is not used in hem_list_alloc_item(),
so remove it.

Link: https://lore.kernel.org/r/20220922123315.3732205-6-xuhaoyue1@hisilicon.com


Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Haoyue Xu <xuhaoyue1@hisilicon.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>