mpeg4videoparse: fix number of bytes read for fixed time increment

The spec I found says "16 bits".
The existing code used log2(somevalue)+1.
ffmpeg uses log2(somevalue-1)+1.
The code now uses log2(somevalue-1)+1, and this makes it work with
some sample video without breaking another sample.
Now, I'm far from certain I've got the right spec, I found it by
searching the internet, so...

https://bugzilla.gnome.org/show_bug.cgi?id=654666

gst/mpeg4videoparse/mpeg4parse.c

@@ -164,8 +164,8 @@ gst_mpeg4_params_parse_vo (MPEG4Params * params, GstBitReader * br)
     int n;
 
     /* Length of the time increment is the minimal number of bits needed to
-     * represent time_increment_resolution */
-    for (n = 0; (time_increment_resolution >> n) != 0; n++);
+     * represent time_increment_resolution-1 */
+    for (n = 0; ((time_increment_resolution - 1) >> n) != 0; n++);
     GET_BITS (br, n, &bits);
 
     fixed_time_increment = bits;