ASoC: ak4118: skip of_device_id table when !CONFIG_OF

The driver can match by multiple methods.  Its of_device_id table is
referenced via of_match_ptr() so it will be unused for !CONFIG_OF
builds:

  sound/soc/codecs/ak4118.c:407:34: warning: ‘ak4118_of_match’ defined but not used [-Wunused-const-variable=]
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20201125164452.89239-15-krzk@kernel.orgSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/ak4118.c

@@ -404,11 +404,13 @@ static int ak4118_i2c_probe(struct i2c_client *i2c,
 				&soc_component_drv_ak4118, &ak4118_dai, 1);
 }
 
+#ifdef CONFIG_OF
 static const struct of_device_id ak4118_of_match[] = {
 	{ .compatible = "asahi-kasei,ak4118", },
 	{}
 };
 MODULE_DEVICE_TABLE(of, ak4118_of_match);
+#endif
 
 static const struct i2c_device_id ak4118_id_table[] = {
 	{ "ak4118", 0 },