ASoC: mediatek: mt8188-mt6359: Cleanup return 0 disguised as return ret

Change all instances of `return ret` to `return 0` at the end of
functions where ret is always zero and also change functions
mt8188_{hdmi,dptx}_codec_init to be consistent with how other
functions are returning errors

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>
Link: https://lore.kernel.org/r/20230608084727.74403-4-angelogioacchino.delregno@collabora.com


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