RDMA/erdma: Use dma_map_page to map scatter MTT buffer

RDMA/erdma: Use dma_map_page to map scatter MTT buffer

Each high-level indirect MTT entry is assumed to point to exactly one page
of the low-level MTT buffer, but dma_map_sg may merge contiguous physical
pages when mapping. To avoid extra overhead from splitting merged regions,
use dma_map_page to map the scatter MTT buffer page by page.

Reviewed-by: Cheng Xu <chengyou@linux.alibaba.com>
Signed-off-by: Boshi Yu <boshiyu@linux.alibaba.com>
Link: https://patch.msgid.link/20250725055410.67520-2-boshiyu@linux.alibaba.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>