ASoC: meson: t9015: mark OF related data as maybe unused

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

sound/soc/meson/t9015.c:315:34: warning: ‘t9015_ids’ defined but not used [-Wunused-const-variable=]

Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

sound/soc/meson/t9015.c

···
 					       &t9015_dai, 1);
 }
 
-static const struct of_device_id t9015_ids[] = {
+static const struct of_device_id t9015_ids[] __maybe_unused = {
 	{ .compatible = "amlogic,t9015", },
 	{ }
 };