avformat: Remove unnecessary inclusions from libavcodec

Also improve the other headers a bit while at it.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavformat/rtpdec_dv.c

@@ -21,10 +21,8 @@
 
 #include "libavutil/avstring.h"
 
-#include "libavcodec/bytestream.h"
-
 #include "avio_internal.h"
-#include "rtpdec_formats.h"
+#include "rtpdec.h"
 
 struct PayloadContext {
     AVIOContext *buf;