HID: asus: support Republic of Gamers special keys

Add support for the special keys found on the internal keyboard of the
Asus Republic of Gamers (ROG) laptop models GL553VD, GL553VE, GL753VD
and GL753VE.

Signed-off-by: Chris Chiu <chiu@endlessm.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>