ARM: dts: Add ARM System timer as clocksource in armv7m

Tested-by: NChanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: NMaxime Coquelin <mcoquelin.stm32@gmail.com>
Signed-off-by: NArnd Bergmann <arnd@arndb.de>

arch/arm/boot/dts/armv7-m.dtsi

@@ -8,6 +8,12 @@
 		reg = <0xe000e100 0xc00>;
 	};
 
+	systick: timer@e000e010 {
+		compatible = "arm,armv7m-systick";
+		reg = <0xe000e010 0x10>;
+		status = "disabled";
+	};
+
 	soc {
 		#address-cells = <1>;
 		#size-cells = <1>;