C2SoftHevcEnc: process QP bounding parameters

The software HEVC encoder now parses the QP bounds passed by the
codec2 framework and uses those values in the codec's configuration.

Bug: 182015210
Test: MediaCodec based application to set qp bounds
      and review the resulting clip's Qp values

Change-Id: I6077807002e6f15ff6e61bf5bfa85ed617777cd7