VFS: fix __start_dirop() kernel-doc warnings

VFS: fix __start_dirop() kernel-doc warnings

Sphinx report kernel-doc warnings:

WARNING: ./fs/namei.c:2853 function parameter 'state' not described in '__start_dirop'
WARNING: ./fs/namei.c:2853 expecting prototype for start_dirop(). Prototype was for __start_dirop() instead

Fix them up.

Fixes: ff7c4ea11a05c8 ("VFS: add start_creating_killable() and start_removing_killable()")
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Link: https://patch.msgid.link/20251219024620.22880-3-bagasdotme@gmail.com
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>