Also match allwinner,sun50i-a64-rtc (present in latest dts import).

Index: sunxi_rtc.c
===================================================================
RCS file: /cvsroot/src/sys/arch/arm/sunxi/sunxi_rtc.c,v
retrieving revision 1.4
diff -u -p -r1.4 sunxi_rtc.c
--- sunxi_rtc.c	16 Jul 2018 23:11:47 -0000	1.4
+++ sunxi_rtc.c	14 Jun 2019 22:04:15 -0000
@@ -128,6 +128,7 @@ static const struct sunxi_rtc_config sun
 
 static const struct of_compat_data compat_data[] = {
 	{ "allwinner,sun4i-a10-rtc",		(uintptr_t)&sun4i_rtc_config },
+	{ "allwinner,sun50i-a64-rtc",		(uintptr_t)&sun6i_rtc_config },
 	{ "allwinner,sun6i-a31-rtc",		(uintptr_t)&sun6i_rtc_config },
 	{ "allwinner,sun7i-a20-rtc",		(uintptr_t)&sun7i_rtc_config },
 	{ NULL }