arm64: dts: meson-g12b-odroid-n2: add sound card

Enable the sound card on the Hardkernel Odroid-N2, enabling HDMI output
using the TDM interface B, being aligned on other boards sound cards.

The internal DAC connected to the audio jack will be added later on, when
driver support is added.

Tested by running:
tinymix set "FRDDR_A SRC 1 EN Switch" 1
tinymix set "FRDDR_A SINK 1 SEL" "OUT 1"
tinymix set "FRDDR_B SRC 1 EN Switch" 1
tinymix set "FRDDR_B SINK 1 SEL" "OUT 1"
tinymix set "FRDDR_C SRC 1 EN Switch" 1
tinymix set "FRDDR_C SINK 1 SEL" "OUT 1"
tinymix set "TOHDMITX I2S SRC" "I2S B"
tinymix set "TOHDMITX Switch" 1

then:
tinymix set "TDMOUT_B SRC SEL" "IN 0"
speaker-test -Dhw:0,0 -c2

then:
tinymix set "TDMOUT_B SRC SEL" "IN 1"
speaker-test -Dhw:0,1 -c2

then:
tinymix set "TDMOUT_B SRC SEL" "IN 2"
speaker-test -Dhw:0,2 -c2

testing HDMI audio output from the all 3 ASoC playback interfaces.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>