arm64: dts: allwinner: pinephone: Support volume key wakeup

PinePhone volume keys are connected to the LRADC in the A64. Users may
want to use them to wake the device from sleep. Support this by
declaring the LRADC as a wakeup source.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20210113040542.34247-4-samuel@sholland.org