ARM: dts: meson: Add the AIU audio controller

Add the AIU audio controller to the Amlogic Meson6/8/8b/8m2 SoC DT. This
provides I2S and SPDIF outputs as well as codec glues for the internal
HDMI controller.
Also add the clock inputs and pin mux definitions on Meson8/8b/8m2. On
Meson6 this is omitted because we neither have a clock nor pin
controller node there yet.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/20210717233030.331273-2-martin.blumenstingl@googlemail.com