rtc: sd3078: quiet maybe-unused variable warning

When CONFIG_OF is disabled then the matching table is not referenced.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210202112219.3610853-22-alexandre.belloni@bootlin.com

drivers/rtc/rtc-sd3078.c

@@ -207,7 +207,7 @@ static const struct i2c_device_id sd3078_id[] = {
 };
 MODULE_DEVICE_TABLE(i2c, sd3078_id);
 
-static const struct of_device_id rtc_dt_match[] = {
+static const __maybe_unused struct of_device_id rtc_dt_match[] = {
 	{ .compatible = "whwave,sd3078" },
 	{},
 };