[nrf fromlist] dts: arm: nordic: Define power states for nrf54h20/cpuapp

Add definition of low power states 'idle' and 's2ram'
for nrf54h20/cpuapp.

Upstream PR: zephyrproject-rtos/zephyr#79098

Signed-off-by: Sebastian Głąb <sebastian.glab@nordicsemi.no>

dts/common/nordic/nrf54h20.dtsi

@@ -28,6 +28,7 @@
 			device_type = "cpu";
 			clocks = <&cpuapp_hsfll>;
 			clock-frequency = <DT_FREQ_M(320)>;
+			cpu-power-states = <&idle &s2ram>;
 		};
 
 		cpurad: cpu@3 {
@@ -72,6 +73,20 @@
 				nordic,tasks-mask = <0xfffffff0>;
 			};
 		};
+
+		power-states {
+			idle: idle {
+				compatible = "zephyr,power-state";
+				power-state-name = "suspend-to-idle";
+				min-residency-us = <100000>;
+			};
+
+			s2ram: s2ram {
+				compatible = "zephyr,power-state";
+				power-state-name = "suspend-to-ram";
+				min-residency-us = <800000>;
+			};
+		};
 	};
 
 	reserved-memory {