arm64: allwinner: a64: add r_ccu node

A64 SoC have a CCU (r_ccu) in PRCM block.

Add the device node for it.

The mux 3 of R_CCU is an internal oscillator, which is 16MHz according
to the user manual, and has only 30% accuracy based on our experience
on older SoCs. The real mesaured value of it on two Pine64 boards is
around 11MHz, which is around 70% of 16MHz.
Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

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

@@ -98,6 +98,14 @@ osc32k: osc32k_clk {
 		clock-output-names = "osc32k";
 	};
 
+	iosc: internal-osc-clk {
+		#clock-cells = <0>;
+		compatible = "fixed-clock";
+		clock-frequency = <16000000>;
+		clock-accuracy = <300000000>;
+		clock-output-names = "iosc";
+	};
+
 	psci {
 		compatible = "arm,psci-0.2";
 		method = "smc";
@@ -392,5 +400,14 @@ rtc: rtc@1f00000 {
 			interrupts = <GIC_SPI 40 IRQ_TYPE_LEVEL_HIGH>,
 				     <GIC_SPI 41 IRQ_TYPE_LEVEL_HIGH>;
 		};
+
+		r_ccu: clock@1f01400 {
+			compatible = "allwinner,sun50i-a64-r-ccu";
+			reg = <0x01f01400 0x100>;
+			clocks = <&osc24M>, <&osc32k>, <&iosc>;
+			clock-names = "hosc", "losc", "iosc";
+			#clock-cells = <1>;
+			#reset-cells = <1>;
+		};
 	};
 };