libavformat/avienc: Make unchanged function arguments const

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/avienc.c

@@ -70,7 +70,7 @@ typedef struct  {
     AVIIndex indexes;
 } AVIStream;
 
-static inline AVIIentry *avi_get_ientry(AVIIndex *idx, int ent_id)
+static inline AVIIentry *avi_get_ientry(const AVIIndex *idx, int ent_id)
 {
     int cl = ent_id / AVI_INDEX_CLUSTER_SIZE;
     int id = ent_id % AVI_INDEX_CLUSTER_SIZE;