staging: iio: ad9834: add of_device_id table

Add a of_device_id struct array of_match_table variable and subsequent
call to MODULE_DEVICE_TABLE macro to enable explicit device tree support.

Co-developed-by: Thiago L. A. Miller <tmiller@mochsl.org.br>
Signed-off-by: Thiago L. A. Miller <tmiller@mochsl.org.br>
Co-developed-by: Osvaldo M. Yasuda <omyasuda@yahoo.com.br>
Signed-off-by: Osvaldo M. Yasuda <omyasuda@yahoo.com.br>
Signed-off-by: João Victor Marques de Oliveira <joao.marques.oliveira@usp.br>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/staging/iio/frequency/ad9834.c

@@ -521,9 +521,20 @@ static const struct spi_device_id ad9834_id[] = {
 };
 MODULE_DEVICE_TABLE(spi, ad9834_id);
 
+static const struct of_device_id ad9834_of_match[] = {
+	{.compatible = "adi,ad9833"},
+	{.compatible = "adi,ad9834"},
+	{.compatible = "adi,ad9837"},
+	{.compatible = "adi,ad9838"},
+	{}
+};
+
+MODULE_DEVICE_TABLE(of, ad9834_of_match);
+
 static struct spi_driver ad9834_driver = {
 	.driver = {
 		.name	= "ad9834",
+		.of_match_table = ad9834_of_match
 	},
 	.probe		= ad9834_probe,
 	.remove		= ad9834_remove,