HID: asus: add ROG Ally N-Key ID and keycodes

A handful of buttons on the ROG Ally are not actually part of the xpad
device and are instead keyboard keys (a typical use of the MCU that asus
uses). We attach a group of F<num> key codes which aren't used much and
which the handheld community has already accepted as defaults here.

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