avformat/movenc, segafilmenc: Remove unnecessary avio_tell()

When the faststart option for the mov/mp4 muxer is used, the current
position (i.e. the size of the already written data pre-shifting) was
evaluated twice: First in an initialization and then again later,
overwriting the first value without having ever touched it. So remove
the initialization.

Also, the clone of this code in the Sega FILM muxer behaves the same and
has been treated the same.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/movenc.c

@@ -6720,7 +6720,7 @@ static int shift_data(AVFormatContext *s)
 {
     int ret = 0, moov_size;
     MOVMuxContext *mov = s->priv_data;
-    int64_t pos, pos_end = avio_tell(s->pb);
+    int64_t pos, pos_end;
     uint8_t *buf, *read_buf[2];
     int read_buf_id = 0;
     int read_size[2];

libavformat/segafilmenc.c

@@ -212,7 +212,7 @@ static int film_init(AVFormatContext *format_context)
 static int shift_data(AVFormatContext *format_context, int64_t shift_size)
 {
     int ret = 0;
-    int64_t pos, pos_end = avio_tell(format_context->pb);
+    int64_t pos, pos_end;
     uint8_t *buf, *read_buf[2];
     int read_buf_id = 0;
     int read_size[2];