platform/x86: x86-android-tablets: Create a platform_device from module_init()

Create a platform_device from module_init() and change
x86_android_tablet_init() / cleanup() into platform_device
probe() and remove() functions.

This is a preparation patch for refactoring x86_android_tablet_get_gpiod()
to no longer use gpiolib private functions like gpiochip_find().

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20230909141816.58358-6-hdegoede@redhat.com