power: avs: Add support for CPR (Core Power Reduction)

CPR (Core Power Reduction) is a technology that reduces core
power on a CPU or other device. It reads voltage settings in
efuse from product test process as initial settings and populates
OPPs for the device being "monitored". Each OPP corresponds to a
"corner" that has a range of valid voltages for a particular
frequency. While the device is running at a particular frequency,
CPR monitors dynamic factors such as temperature, etc. and
adjusts the voltage for that frequency accordingly to save power
and meet silicon characteristic requirements.

This driver is based on work by others on codeaurora.org[1].

[1] https://www.codeaurora.org/cgit/quic/la/kernel/msm-3.10/tree/drivers/regulator/cpr-regulator.c?h=msm-3.10



Cc: <devicetree@vger.kernel.org>
Cc: David Collins <collinsd@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>