platform/x86: lenovo-yogabook: Add keyboard backlight control to platform driver

On the Android yb1-x90f/l models there is not ACPI method to control
the keyboard backlight brightness. Instead the second PWM controller
is exposed directly to the OS there.

Add support for controlling keyboard backlight brightness on the Android
model by using the PWM subsystem to directly control the PWM.

The Android model also requires explicitly turning the backlight off
on suspend, which on the Windows model was done automatically.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20230430165807.472798-19-hdegoede@redhat.com