fanotify: fix collision of internal and uapi mark flags

The new mark flag FAN_MARK_FILESYSTEMS collides with existing internal
flag FAN_MARK_ONDIR. Change internal flag value to avoid the collision.

Fixes: d54f4fba

 ("fanotify: add API to attach/detach super block mark")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>