staging: iio: spear_adc: Add missing CONFIG_OF macro

The data structure is required only when DT is enabled.
Hence compile it conditionally.
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Acked-by: Stefan Roese <sr@denx.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/adc/spear_adc.c

@@ -415,11 +415,13 @@ static int spear_adc_remove(struct platform_device *pdev)
 	return 0;
 }
 
+#ifdef CONFIG_OF
 static const struct of_device_id spear_adc_dt_ids[] = {
 	{ .compatible = "st,spear600-adc", },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, spear_adc_dt_ids);
+#endif
 
 static struct platform_driver spear_adc_driver = {
 	.probe		= spear_adc_probe,