dts: stm32: add STGEN node in stm32mp251.dtsi

Add the STGEN node in the stm32mp251.dtsi SoC device tree file and
default enable it as it is the source for the ARM generic timer
of the ARM cortexA35.

Signed-off-by: Gatien Chevallier <[email protected]>

core/arch/arm/dts/stm32mp251.dtsi

@@ -469,6 +469,13 @@
 			status = "disabled";
 		};
 
+		stgenc: stgen@48080000 {
+			compatible = "st,stm32mp25-stgen";
+			reg = <0x48080000 0x1000>;
+			clocks = <&rcc CK_BUS_STGEN>, <&rcc CK_KER_STGEN>;
+			clock-names = "bus", "stgen_clk";
+		};
+
 		fmc: memory-controller@48200000 {
 			#address-cells = <2>;
 			#size-cells = <1>;