Qualcomm OPP bindings to describe OPP nodes

The bindings are based on top of the operating-points-v2 bindings
described in Documentation/devicetree/bindings/opp/opp.txt
Additional properties are described below.

* OPP Table Node

Required properties:
- compatible: Allow OPPs to express their compatibility. It should be:
  "operating-points-v2-qcom-level"

* OPP Node

Required properties:
- qcom,opp-fuse-level: A positive value representing the fuse corner/level
  associated with this OPP node. Sometimes several corners/levels shares
  a certain fuse corner/level. A fuse corner/level contains e.g. ref uV,
  min uV, and max uV.