ARM: dts: msm: Add the energy-model for SDM670

The energy-model is needed for Energy-aware scheduler (EAS)
to place the tasks on optimal CPUs to maximize the energy
efficiency.

Change-Id: I2136137b8db4b52b28e6998b7e8ceb199a49bef8
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>