ASoC: sta529: Add OF device ID table

The driver doesn't have a struct of_device_id table but supported devices
are registered via Device Trees. This is working on the assumption that a
I2C device registered via OF will always match a legacy I2C device ID and
that the MODALIAS reported will always be of the form i2c:<device>.

But this could change in the future so the correct approach is to have an
OF device ID table if the devices are registered via OF.

Before this patch:

$ modinfo sound/soc/codecs/snd-soc-sta529.ko | grep alias
alias:          i2c:sta529

After this patch:

$ modinfo sound/soc/codecs/snd-soc-sta529.ko | grep alias
alias:          of:N*T*Cst,sta529C*
alias:          of:N*T*Cst,sta529
alias:          i2c:sta529
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/sta529.c

@@ -375,9 +375,16 @@ static const struct i2c_device_id sta529_i2c_id[] = {
 };
 MODULE_DEVICE_TABLE(i2c, sta529_i2c_id);
 
+static const struct of_device_id sta529_of_match[] = {
+	{ .compatible = "st,sta529", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, sta529_of_match);
+
 static struct i2c_driver sta529_i2c_driver = {
 	.driver = {
 		.name = "sta529",
+		.of_match_table = sta529_of_match,
 	},
 	.probe		= sta529_i2c_probe,
 	.remove		= sta529_i2c_remove,