ASoC: inno_rk3036: mark OF related data as maybe unused

The driver can be compile tested with !CONFIG_OF making certain data
unused:

  sound/soc/codecs/inno_rk3036.c:470:34: warning: ‘rk3036_codec_of_match’ defined but not used [-Wunused-const-variable=]
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20201125164452.89239-5-krzk@kernel.orgSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/inno_rk3036.c

@@ -467,7 +467,7 @@ static int rk3036_codec_platform_remove(struct platform_device *pdev)
 	return 0;
 }
 
-static const struct of_device_id rk3036_codec_of_match[] = {
+static const struct of_device_id rk3036_codec_of_match[] __maybe_unused = {
 	{ .compatible = "rockchip,rk3036-codec", },
 	{}
 };