ARM: dts: meson8b: ec100: enable the RTC

The RTC is always enabled on this board since the battery is already
connected in the factory.
According to the schematics the VCC_RTC regulator (which is either
powered by the internal 3.3V or a battery) is connected to the 0.9V
RTC_VDD input of the SoCs.

Signed-off-by: Martin Blumenstingl <[e-mail]>
Signed-off-by: Kevin Hilman <[e-mail]>

arch/arm/boot/dts/meson8b-ec100.dts

···
 		};
 	};
 
+	rtc32k_xtal: rtc32k-xtal-clk {
+		/* X2 in the schematics */
+		compatible = "fixed-clock";
+		clock-frequency = <32768>;
+		clock-output-names = "RTC32K";
+		#clock-cells = <0>;
+	};
+
 	usb_vbus: regulator-usb-vbus {
 		/*
 		 * Silergy SY6288CCAC-GP 2A Power Distribution Switch.
···
 	pinctrl-names = "default";
 	clocks = <&clkc CLKID_XTAL>;
 	clock-names = "clkin0";
+};
+
+&rtc {
+	status = "okay";
+	clocks = <&rtc32k_xtal>;
+	vdd-supply = <&vcc_rtc>;
 };
 
 /* exposed through the pin headers labeled "URDUG1" on the top of the PCB */