cpuidle: psci: Support hierarchical CPU idle states

Currently CPU's idle states are represented using the flattened model.
Let's add support for the hierarchical layout, via converting to use
of_get_cpu_state_node().

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>

drivers/cpuidle/cpuidle-psci.c

@@ -86,8 +86,7 @@ static int __init psci_dt_cpu_init_idle(struct device_node *cpu_node,
 		return -ENOMEM;
 
 	for (i = 1; i < state_count; i++) {
-		state_node = of_parse_phandle(cpu_node, "cpu-idle-states",
-					      i - 1);
+		state_node = of_get_cpu_state_node(cpu_node, i - 1);
 		if (!state_node)
 			break;