ASoC: ti: davinci: mark OF related data as maybe unused

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

  sound/soc/ti/davinci-i2s.c:750:34: warning: ‘davinci_i2s_match’ defined but not used [-Wunused-const-variable=]
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20201125164452.89239-13-krzk@kernel.orgSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/ti/davinci-i2s.c

@@ -747,7 +747,7 @@ static int davinci_i2s_remove(struct platform_device *pdev)
 	return 0;
 }
 
-static const struct of_device_id davinci_i2s_match[] = {
+static const struct of_device_id davinci_i2s_match[] __maybe_unused = {
 	{ .compatible = "ti,da850-mcbsp" },
 	{},
 };