mfd: retu: 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 a
OF device ID table if the devices are registered via OF.

Signed-off-by: Javier Martinez Canillas <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Acked-by: Aaro Koskinen <[e-mail]>
Acked-by: Tony Lindgren <[e-mail]>
Reviewed-by: Wolfram Sang <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>

drivers/mfd/retu-mfd.c

···
 };
 MODULE_DEVICE_TABLE(i2c, retu_id);
 
+static const struct of_device_id retu_of_match[] = {
+	{ .compatible = "nokia,retu" },
+	{ .compatible = "nokia,tahvo" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, retu_of_match);
+
 static struct i2c_driver retu_driver = {
 	.driver		= {
 		.name = "retu-mfd",
+		.of_match_table = retu_of_match,
 	},
 	.probe		= retu_probe,
 	.remove		= retu_remove,