ASoC: intel, keembay-i2s: Fix a dt_binding_check warning

ASoC: intel, keembay-i2s: Fix a dt_binding_check warning

The property "dmas" contains two items: DMA "TX" and "RX" channel,
Therefore, its value also needs to be written in two parts.

Otherwise, below YAML check warning is reported:
Documentation/devicetree/bindings/sound/intel,keembay-i2s.example.dt.yaml:\
i2s@20140000: dmas: [[4294967295, 29, 4294967295, 33]] is too short

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210329081435.2200-1-thunder.leizhen@huawei.com
Signed-off-by: Mark Brown <broonie@kernel.org>