dts: arm: nordic: Add power states for nRF54H20

Add `idle` and `s2ram` power states for nRF54H20 cpuapp and cpurad.
Also the substate `idle_cache_disable` added.

Signed-off-by: Adam Kondraciuk <adam.kondraciuk@nordicsemi.no>

dts/common/nordic/nrf54h20.dtsi

@@ -28,7 +28,7 @@
 			device_type = "cpu";
 			clocks = <&cpuapp_hsfll>;
 			clock-frequency = <DT_FREQ_M(320)>;
-			cpu-power-states = <&idle &s2ram>;
+			cpu-power-states = <&idle_cache_disabled &s2ram>;
 		};
 
 		cpurad: cpu@3 {
@@ -37,6 +37,7 @@
 			device_type = "cpu";
 			clocks = <&cpurad_hsfll>;
 			clock-frequency = <DT_FREQ_M(256)>;
+			cpu-power-states = <&idle_cache_disabled>;
 		};
 
 		cpuppr: cpu@d {
@@ -125,12 +126,14 @@
 		};
 
 		power-states {
-			idle: idle {
+			// substate-id = <0>; is reserved for "idle", cache powered on
+			// substate-id = <1>; is reserved for "idle-cache-retained"
+			idle_cache_disabled: idle_cache_disabled {
 				compatible = "zephyr,power-state";
 				power-state-name = "suspend-to-idle";
+				substate-id = <2>;
 				min-residency-us = <100000>;
 			};
-
 			s2ram: s2ram {
 				compatible = "zephyr,power-state";
 				power-state-name = "suspend-to-ram";