Fix two identical warnings when compiling riff.c and nuv.c with icc:

warning #188: enumerated type mixed with another type

Originally committed as revision 16281 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/riff.c

@@ -425,9 +425,9 @@ void get_wav_header(ByteIOContext *pb, AVCodecContext *codec, int size)
 }
 
 
-int wav_codec_get_id(unsigned int tag, int bps)
+enum CodecID wav_codec_get_id(unsigned int tag, int bps)
 {
-    int id;
+    enum CodecID id;
     id = codec_get_id(codec_wav_tags, tag);
     if (id <= 0)
         return id;

libavformat/riff.h

@@ -41,7 +41,7 @@ typedef struct AVCodecTag {
 
 void put_bmp_header(ByteIOContext *pb, AVCodecContext *enc, const AVCodecTag *tags, int for_asf);
 int put_wav_header(ByteIOContext *pb, AVCodecContext *enc);
-int wav_codec_get_id(unsigned int tag, int bps);
+enum CodecID wav_codec_get_id(unsigned int tag, int bps);
 void get_wav_header(ByteIOContext *pb, AVCodecContext *codec, int size);
 
 extern const AVCodecTag codec_bmp_tags[];