avformat: fix typo in comment

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavformat/avformat.h

@@ -581,7 +581,7 @@ enum AVStreamParseType {
     AVSTREAM_PARSE_FULL_ONCE,  /**< full parsing and repack of the first frame only, only implemented for H.264 currently */
     AVSTREAM_PARSE_FULL_RAW=MKTAG(0,'R','A','W'),       /**< full parsing and repack with timestamp and position generation by parser for raw
                                                              this assumes that each packet in the file contains no demuxer level headers and
-                                                             just codec level data, otherwise position generaion would fail */
+                                                             just codec level data, otherwise position generation would fail */
 };
 
 typedef struct AVIndexEntry {