arm64: dts: allwinner: pinephone: Add Bluetooth support

The PinePhone has a Realtek rtl8723cs Bluetooth controller.

Signed-off-by: Ondrej Jirman <megous@megous.com>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20201105054135.24860-7-samuel@sholland.org