arm64: allwinner: a64: Add RTC clock to phandle 32kHz external oscillator

Outside of SOC few chips need external clock source
through RTC example Wifi chip. So RTC clock nodes to
phandle 32kHz external oscillator.

prefix rtc- with clock-output-names defined in
dt-binding to avoid confusion with existing osc32k name.
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>

arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi

@@ -634,6 +634,9 @@ rtc: rtc@1f00000 {
 			reg = <0x01f00000 0x54>;
 			interrupts = <GIC_SPI 40 IRQ_TYPE_LEVEL_HIGH>,
 				     <GIC_SPI 41 IRQ_TYPE_LEVEL_HIGH>;
+			clock-output-names = "rtc-osc32k", "rtc-osc32k-out";
+			clocks = <&osc32k>;
+			#clock-cells = <1>;
 		};
 
 		r_intc: interrupt-controller@1f00c00 {