HID: asus: Add support for ASUS N-Key keyboard

The ASUS N-Key keyboard uses the productId of 0x1866 and is used in
almost all modern ASUS gaming laptops with slight changes to the
firmware. This patch enables: Fn+key hotkeys, keyboard backlight
brightness control.

Additionally this keyboard requires the LED interface to be
initialized before such things as keyboard backlight control work.

Signed-off-by: Luke D Jones <luke@ljones.dev>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>