drivers: thermal: cpu_voltage: Add CPU voltage cooling device support

A single CPU cluster can have CPUs with different frequency plans.
Mitigating individual CPU may or may not bring down the CPU cluster
voltage depending on the operating level of the other CPUs.

CPU voltage cooling device will provide support to apply CPU frequency
mitigation on different CPUs in a cluster to achieve a reduction in
cluster voltage. This is achieved by building a mitigation table mapping
the frequency of different CPUs based on voltage.

Change-Id: Ie09375c6c15a9f81e663fca96c5af87e0b6789c2
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>