RDMA/rtrs: Fix clt_path::max_pages_per_mr calculation

RDMA/rtrs: Fix clt_path::max_pages_per_mr calculation

If device max_mr_size bits in the range [mr_page_shift+31:mr_page_shift]
are zero, the `min3` function will set clt_path::max_pages_per_mr to
zero.

`alloc_path_reqs` will pass zero, which is invalid, as the third parameter
to `ib_alloc_mr`.

Fixes: 6a98d71daea1 ("RDMA/rtrs: client: main functionality")
Signed-off-by: Honggang LI <honggangli@163.com>
Link: https://patch.msgid.link/20251229025617.13241-1-honggangli@163.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>