arm64: dts: meson: g12: add internal DAC

add internal audio DAC support on the g12 and sm1 SoC family

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Link: https://lore.kernel.org/r/20200506221656.477379-7-jbrunet@baylibre.com