qcom: clock-cpu-8994: Introduce a CPU scaling driver for the MSM8994

Introduce a driver that models the cluster and CCI
clock trees in the MSM8994, and provides clocks to
various drivers that decide the frequency of those
clocks.

Change-Id: I63da505d159bb2bb1cddbd8dfba747a07ea9fd27
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>