arm64: dts: meson: add audio playback to nanopi-k2

Add initial audio support limited to HDMI i2s.

Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Acked-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Link: https://lore.kernel.org/r/20201203060023.9454-5-christianshewitt@gmail.com