RDMA/hns: Simplify 'struct hns_roce_hem' allocation

RDMA/hns: Simplify 'struct hns_roce_hem' allocation

'struct hns_roce_hem' is used to refer to the last level of
dma buffer managed by the hw, pointed by a single BA(base
address) in the previous level of BT(base table), so the dma
buffer in 'struct hns_roce_hem' must be contiguous.

Right now the size of dma buffer in 'struct hns_roce_hem' is
decided by mhop->buf_chunk_size in get_hem_table_config(),
which ensure the mhop->buf_chunk_size is power of two of
PAGE_SIZE, so there will be only one contiguous dma buffer
allocated in hns_roce_alloc_hem(), which means hem->chunk_list
and chunk->mem for linking multi dma buffers is unnecessary.

This patch removes the hem->chunk_list and chunk->mem and other
related macro and function accordingly.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
Link: https://lore.kernel.org/r/20240113085935.2838701-7-huangjunxian6@hisilicon.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>