ASoC: dt-bindings: Do not override firmware-name $ref

dtschema package defines firmware-name as string-array, so individual
bindings should not make it a string but instead just narrow the number
of expected firmware file names.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://msgid.link/r/20240115182017.1610055-1-krzysztof.kozlowski@linaro.org


Signed-off-by: Mark Brown <broonie@kernel.org>