rtc: rx8581: 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/20210202112219.3610853-20-alexandre.belloni@bootlin.com

drivers/rtc/rtc-rx8581.c

@@ -314,7 +314,7 @@ static const struct i2c_device_id rx8581_id[] = {
 };
 MODULE_DEVICE_TABLE(i2c, rx8581_id);
 
-static const struct of_device_id rx8581_of_match[] = {
+static const __maybe_unused struct of_device_id rx8581_of_match[] = {
 	{ .compatible = "epson,rx8571", .data = &rx8571_config },
 	{ .compatible = "epson,rx8581", .data = &rx8581_config },
 	{ /* sentinel */ }