RDMA/hns: Initialize seqfile before creating file

RDMA/hns: Initialize seqfile before creating file

The debugfs file was created before seq->read and seq->data were set,
leaving a small window where userspace could access an uninitialized
seqfile.

Move debugfs_create_file() after the assignments to avoid this issue.
Also, inline the original init_debugfs_seqfile() since it is not a
really necessary helper.

Fixes: ca7ad04cd5d2 ("RDMA/hns: Add debugfs to hns RoCE")
Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
Link: https://patch.msgid.link/20260507012148.1079712-2-huangjunxian6@hisilicon.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>