arm64: dts: add clock support for all the cpus

This patch adds the CPU clocks so that the CPU DVFS can be enabled.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Liviu Dudau <Liviu.Dudau@arm.com>
Cc: Jon Medhurst (Tixy) <tixy@linaro.org>