ARM: dts: msm: add initial device tree for Lahaina low power modes

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