arm64: dts: juno: Add idle-states to device tree

This patch adds idle-states bindings data collected through a set of
benchmarking experiments (latency and energy consumption) on Juno
boards. Latencies data represents the worst case scenarios as required
by the DT idle-states bindings.

Signed-off-by: Jon Medhurst <tixy@linaro.org>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Olof Johansson <olof@lixom.net>