Almost every board machine / sound cards has "audio-routing" and "model"
properties, so move them to common schema to have only one definition of
these properties.

For amlogic,gx-sound-card, drop the minItems: 2 from the
"audio-routing", because any limit here - lower or upper- is rather
meaningless.  This will also fix `dtbs_check` warnings like:

  meson-gxm-s912-libretech-pc.dtb: sound: audio-routing: ['AU2 INL', 'ACODEC LOLN', 'AU2 INR', 'ACODEC LORN', '7J4-14 LEFT', 'AU2 OUTL', '7J4-11 RIGHT', 'AU2 OUTR'] is too long
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230810063300.20151-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Mark Brown <broonie@kernel.org>