arm64: dts: rockchip: Enable HDMI audio on BPI R2 Pro

This enables the i2s0 controller and the hdmi-sound node on
the Bananapi R2 Pro single-board computer.

Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Link: https://lore.kernel.org/r/20220606170803.478082-4-linux@fw-web.de
Signed-off-by: Heiko Stuebner <heiko@sntech.de>