Use PIX_FMT_NONE to silence icc warning #188:

enumerated type mixed with another type


git-svn-id: file:///var/local/repositories/ffmpeg/trunk@15942 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavfilter/avfilter.c

@@ -90,7 +90,7 @@ int avfilter_link(AVFilterContext *src, unsigned srcpad,
     link->dst     = dst;
     link->srcpad  = srcpad;
     link->dstpad  = dstpad;
-    link->format  = -1;
+    link->format  = PIX_FMT_NONE;
 
     return 0;
 }