openmax: add OMX_IndexConfigOperatingRate.

Bug: 19620911
Change-Id: I4458705414ab0087bbfd60dee201973045cd711b
diff --git a/include/media/openmax/OMX_AsString.h b/include/media/openmax/OMX_AsString.h
index dbcecf5..7856c06 100644
--- a/include/media/openmax/OMX_AsString.h
+++ b/include/media/openmax/OMX_AsString.h
@@ -522,6 +522,7 @@
 //      case OMX_IndexParamSliceSegments:               return "ParamSliceSegments";
         case OMX_IndexConfigAutoFramerateConversion:    return "ConfigAutoFramerateConversion";
         case OMX_IndexConfigPriority:                   return "ConfigPriority";
+        case OMX_IndexConfigOperatingRate:              return "ConfigOperatingRate";
         default:                                        return asString((OMX_INDEXTYPE)i, def);
     }
 }