avcodec/codec: use the correct name for all AVCodec.decode() parameters

This field hasn't been used to return the output frame size since
avcodec_decode_audio4() was introduced.

Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/codec.h

@@ -281,7 +281,8 @@ typedef struct AVCodec {
      */
     int (*encode2)(struct AVCodecContext *avctx, struct AVPacket *avpkt,
                    const struct AVFrame *frame, int *got_packet_ptr);
-    int (*decode)(struct AVCodecContext *, void *outdata, int *outdata_size, struct AVPacket *avpkt);
+    int (*decode)(struct AVCodecContext *avctx, void *outdata,
+                  int *got_frame_ptr, struct AVPacket *avpkt);
     int (*close)(struct AVCodecContext *);
     /**
      * Encode API with decoupled frame/packet dataflow. This function is called