ARM64: zynqmp: Add idle state for ZynqMP

Added the idle-states node to describe zynqmp idle states. Only cpu-sleep-0
idle state is added in this patch. References to the idle-states node are
added in all CPU nodes. Time values: entry/exit latencies and min-residency,
needs to be tuned. arm,psci-suspend-param is selected to comply with PSCIv1.0
and Extended StateID format.

Signed-off-by: Stefan Krsmanovic <stefan.krsmanovic@aggios.com>
Acked-by: Will Wong <willw@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/arm/dts/zynqmp.dtsi

@@ -22,6 +22,7 @@
 			device_type = "cpu";
 			enable-method = "psci";
 			reg = <0x0>;
+			cpu-idle-states = <&CPU_SLEEP_0>;
 		};
 
 		cpu@1 {
@@ -29,6 +30,7 @@
 			device_type = "cpu";
 			enable-method = "psci";
 			reg = <0x1>;
+			cpu-idle-states = <&CPU_SLEEP_0>;
 		};
 
 		cpu@2 {
@@ -36,6 +38,7 @@
 			device_type = "cpu";
 			enable-method = "psci";
 			reg = <0x2>;
+			cpu-idle-states = <&CPU_SLEEP_0>;
 		};
 
 		cpu@3 {
@@ -43,6 +46,20 @@
 			device_type = "cpu";
 			enable-method = "psci";
 			reg = <0x3>;
+			cpu-idle-states = <&CPU_SLEEP_0>;
+		};
+
+		idle-states {
+			entry-mehod = "arm,psci";
+
+			CPU_SLEEP_0: cpu-sleep-0 {
+				compatible = "arm,idle-state";
+				arm,psci-suspend-param = <0x40000000>;
+				local-timer-stop;
+				entry-latency-us = <300>;
+				exit-latency-us = <600>;
+				min-residency-us = <800000>;
+			};
 		};
 	};