ASoC: wm8974: add devicetree support

This adds devicetree support to the wm8974 codec driver.
With a DT-based kernel, there is no board-specific setting
to select the driver so allow it to be manually chosen.

Signed-off-by: Mans Rullgard <[e-mail]>
Acked-by: Charles Keepax <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

sound/soc/codecs/Kconfig

···
 	tristate
 
 config SND_SOC_WM8974
-	tristate
+	tristate "Wolfson Microelectronics WM8974 codec"
+	depends on I2C
 
 config SND_SOC_WM8978
 	tristate "Wolfson Microelectronics WM8978 codec"

sound/soc/codecs/wm8974.c

···
 };
 MODULE_DEVICE_TABLE(i2c, wm8974_i2c_id);
 
+static const struct of_device_id wm8974_of_match[] = {
+       { .compatible = "wlf,wm8974", },
+       { }
+};
+MODULE_DEVICE_TABLE(of, wm8974_of_match);
+
 static struct i2c_driver wm8974_i2c_driver = {
 	.driver = {
 		.name = "wm8974",
+		.of_match_table = wm8974_of_match,
 	},
 	.probe =    wm8974_i2c_probe,
 	.remove =   wm8974_i2c_remove,