dt-bindings: cpufreq: Document operating-points-v2-krait-cpu

In Certain QCOM SoCs like ipq8064, apq8064, msm8960, msm8974
that has KRAIT processors the voltage/current value of each OPP
varies based on the silicon variant in use.
operating-points-v2-krait-cpu specifies the phandle to nvmem efuse cells
and the operating-points-v2 table for each opp. The qcom-cpufreq driver
reads the efuse value from the SoC to provide the required information
that is used to determine the voltage and current value for each OPP of
operating-points-v2 table when it is parsed by the OPP framework.

Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Sricharan R <sricharan@codeaurora.org>