ASoC: wm8940: add devicetree support

This adds devicetree support to the wm8940 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: Lukasz Majewski <lukma@denx.de>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20220509121055.31103-1-lukma@denx.deSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/Kconfig

@@ -1868,7 +1868,7 @@ config SND_SOC_WM8904
 	depends on I2C
 
 config SND_SOC_WM8940
-	tristate
+	tristate "Wolfson Microelectronics WM8940 codec"
 	depends on I2C
 
 config SND_SOC_WM8955

sound/soc/codecs/wm8940.c

@@ -778,9 +778,16 @@ static const struct i2c_device_id wm8940_i2c_id[] = {
 };
 MODULE_DEVICE_TABLE(i2c, wm8940_i2c_id);
 
+static const struct of_device_id wm8940_of_match[] = {
+	{ .compatible = "wlf,wm8940", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, wm8940_of_match);
+
 static struct i2c_driver wm8940_i2c_driver = {
 	.driver = {
 		.name = "wm8940",
+		.of_match_table = wm8940_of_match,
 	},
 	.probe_new = wm8940_i2c_probe,
 	.id_table = wm8940_i2c_id,