__fs_parse: Correct a documentation comment

Commit 7f5d3814

 ("new primitive: __fs_parse()")
taking p_log instead of fs_context.

So, update that comment to refer to p_log instead

Signed-off-by: Chen Hanxiao <chenhx.fnst@fujitsu.com>
Link: https://lore.kernel.org/r/20240202072042.906-1-chenhx.fnst@fujitsu.com


Signed-off-by: Christian Brauner <brauner@kernel.org>