rtc: sunxi: Depend on platforms sun4i/sun7i that actually have the rtc

Now that we have Kconfig options for individual sunxi platforms, let
the rtc-sunxi driver depend on the platforms that actually have this
hardware, sun4i and sun7i.
Signed-off-by: NChen-Yu Tsai <wens@csie.org>
Signed-off-by: NMaxime Ripard <maxime.ripard@free-electrons.com>

drivers/rtc/Kconfig

@@ -1184,7 +1184,7 @@ config RTC_DRV_SUN6I
 
 config RTC_DRV_SUNXI
 	tristate "Allwinner sun4i/sun7i RTC"
-	depends on ARCH_SUNXI
+	depends on MACH_SUN4I || MACH_SUN7I
 	help
 	  If you say Y here you will get support for the RTC found on
 	  Allwinner A10/A20.