HID: asus: Filter keyboard EC for old ROG keyboard

Older ROG keyboards emit a similar stream of bytes to the new
N-Key keyboards and require filtering to prevent a lot of
unmapped key warnings showing. As all the ROG keyboards use
QUIRK_USE_KBD_BACKLIGHT this is now used to branch to filtering
in asus_raw_event.

Signed-off-by: Luke D Jones <luke@ljones.dev>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>