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/arm64/boot/dts/xilinx/zynqmp.dtsi

@@ -25,6 +25,7 @@ cpu0: cpu@0 {
 			device_type = "cpu";
 			enable-method = "psci";
 			reg = <0x0>;
+			cpu-idle-states = <&CPU_SLEEP_0>;
 		};
 
 		cpu1: cpu@1 {
@@ -32,6 +33,7 @@ cpu1: cpu@1 {
 			device_type = "cpu";
 			enable-method = "psci";
 			reg = <0x1>;
+			cpu-idle-states = <&CPU_SLEEP_0>;
 		};
 
 		cpu2: cpu@2 {
@@ -39,6 +41,7 @@ cpu2: cpu@2 {
 			device_type = "cpu";
 			enable-method = "psci";
 			reg = <0x2>;
+			cpu-idle-states = <&CPU_SLEEP_0>;
 		};
 
 		cpu3: cpu@3 {
@@ -46,6 +49,20 @@ cpu3: cpu@3 {
 			device_type = "cpu";
 			enable-method = "psci";
 			reg = <0x3>;
+			cpu-idle-states = <&CPU_SLEEP_0>;
+		};
+
+		idle-states {
+			entry-method = "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 = <10000>;
+			};
 		};
 	};