platform/x86: x86-android-tablets: Add gpio_keys support to x86_android_tablet_init()

Add gpio_keys instantation support to x86_android_tablet_init(), to avoid
this having to be repeated in various x86_dev_info.init() functions.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20230301092331.7038-10-hdegoede@redhat.com