Add initial device tree bindings to support CPU and cluster low power
modes on Lahaina. To do low power modes, switch over the enable-method
of the CPU to PSCI. Also add bindings for RPMH, master and DDR stats.
Since PSCI firmware will read the PSCI state id from cpu nodes, add
cpu-idle-states to the cpu DT bindings.
Change-Id: I7d9ef6f89e1a9b0987df3b7511f5b0b5ed627abc