arm64: dts: meson: add audio playback to rbox-pro

Add initial support limited to HDMI i2s and SPDIF (LPCM).

Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/20210914151631.2841-1-christianshewitt@gmail.com