fs: Describe @isnew parameter in ilookup5_nowait()

fs: Describe @isnew parameter in ilookup5_nowait()

Sphinx reports kernel-doc warning:

WARNING: ./fs/inode.c:1607 function parameter 'isnew' not described in 'ilookup5_nowait'

Describe the parameter.

Fixes: a27628f4363435 ("fs: rework I_NEW handling to operate without fences")
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Link: https://patch.msgid.link/20251219024620.22880-2-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>