To enable the OS to better support PSCI OS initiated CPU suspend mode,
let's convert from the flattened layout to the hierarchical layout.

In the hierarchical layout, let's create a power domain provider per CPU
and describe the idle states for each CPU inside the power domain provider
node. To group the CPUs into a cluster, let's add another power domain
provider and make it act as the master domain. Note that, the CPU's idle
states remains compatible with "arm,idle-state", while the cluster's idle
state becomes compatible with "domain-idle-state".
Co-developed-by: Lina Iyer <lina.iyer@linaro.org>
Signed-off-by: Lina Iyer <lina.iyer@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>