arm64: dts: Fix RTC by providing rtc_src clock

Add RTC source clock as Exynos7 needs source (32.768KHz) clock
for RTC block. Without this currently S3C RTC driver probe is broken
on this SoC.
Signed-off-by: Alim Akhtar <alim.akhtar@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm64/boot/dts/exynos/exynos7-espresso.dts

@@ -12,6 +12,7 @@
 /dts-v1/;
 #include "exynos7.dtsi"
 #include <dt-bindings/interrupt-controller/irq.h>
+#include <dt-bindings/clock/samsung,s2mps11.h>
 
 / {
 	model = "Samsung Exynos7 Espresso board based on EXYNOS7";
@@ -43,6 +44,8 @@ &serial_2 {
 
 &rtc {
 	status = "okay";
+	clocks = <&clock_ccore PCLK_RTC>, <&s2mps15_osc S2MPS11_CLK_AP>;
+	clock-names = "rtc", "rtc_src";
 };
 
 &watchdog {