rtc: sun6i: Add R40 compatible

The R40 has a quite different RTC, with only a single interrupt line, but
two clock outputs. Let's add a compatible.
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-sun6i.c

@@ -681,6 +681,7 @@ static const struct of_device_id sun6i_rtc_dt_ids[] = {
 	{ .compatible = "allwinner,sun6i-a31-rtc" },
 	{ .compatible = "allwinner,sun8i-a23-rtc" },
 	{ .compatible = "allwinner,sun8i-h3-rtc" },
+	{ .compatible = "allwinner,sun8i-r40-rtc" },
 	{ .compatible = "allwinner,sun8i-v3-rtc" },
 	{ .compatible = "allwinner,sun50i-h5-rtc" },
 	{ /* sentinel */ },