media: add OMX_VIDEO_CodingDolbyVision.

Bug: 25684127
Change-Id: I4eccb66d679a3dd4ac47556a0d206df2ebf52338
diff --git a/include/media/openmax/OMX_AsString.h b/include/media/openmax/OMX_AsString.h
index ae8430d..c3145c9 100644
--- a/include/media/openmax/OMX_AsString.h
+++ b/include/media/openmax/OMX_AsString.h
@@ -714,6 +714,7 @@
         case OMX_VIDEO_CodingVP8:        return "VP8";
         case OMX_VIDEO_CodingVP9:        return "VP9";
         case OMX_VIDEO_CodingHEVC:       return "HEVC";
+        case OMX_VIDEO_CodingDolbyVision:return "DolbyVision";
         default:                         return def;
     }
 }