dt-bindings: opp: Add qcom-opp bindings with properties needed for CPR

Add qcom-opp bindings with properties needed for Core Power Reduction
(CPR).

CPR is included in a great variety of Qualcomm SoCs, e.g. msm8916 and
msm8996. CPR was first introduced in msm8974.

Changes since RFC:
-Removed opp-hz. It is already an optional property in opp.txt
so no need to specify it with the same definition here.

Co-developed-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
Signed-off-by: Niklas Cassel <niklas.cassel@linaro.org>