arm64: dts: imx8mm: Add system counter node

Add i.MX8MM system counter node to enable timer-imx-sysctr
broadcast timer driver.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

arch/arm64/boot/dts/freescale/imx8mm.dtsi

@@ -510,6 +510,14 @@ pwm4: pwm@30690000 {
 				#pwm-cells = <2>;
 				status = "disabled";
 			};
+
+			system_counter: timer@306a0000 {
+				compatible = "nxp,sysctr-timer";
+				reg = <0x306a0000 0x20000>;
+				interrupts = <GIC_SPI 47 IRQ_TYPE_LEVEL_HIGH>;
+				clocks = <&osc_24m>;
+				clock-names = "per";
+			};
 		};
 
 		aips3: bus@30800000 {