platform/x86: asus-wmi: Implement TUF laptop keyboard LED modes

platform/x86: asus-wmi: Implement TUF laptop keyboard LED modes

Adds support for changing the laptop keyboard LED mode and colour.

The modes are visible effects such as static, rainbow, pulsing,
colour cycles.

These sysfs attributes are added to asus::kbd_backlight:
- kbd_rgb_mode
- kbd_rgb_mode_index

Signed-off-by: Luke D. Jones <luke@ljones.dev>
Link: https://lore.kernel.org/r/20220825232251.345893-2-luke@ljones.dev
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>