fanotify: reserve event bit of deprecated FAN_DIR_MODIFY

Avoid reusing it, because we would like to reserve it for future
FAN_PATH_MODIFY pre-content event.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/632d9f80428e2e7a6b6a8ccc2925d87c92bbb518.1731684329.git.josef@toxicpanda.com