avcodec: Add more missing #includes for ff_get_buffer()

libavcodec/libgsm.c

@@ -30,6 +30,7 @@
 #include <gsm/gsm.h>
 
 #include "avcodec.h"
+#include "internal.h"
 #include "gsm.h"
 
 static av_cold int libgsm_encode_init(AVCodecContext *avctx) {

libavcodec/libopencore-amr.c

@@ -20,6 +20,7 @@
  */
 
 #include "avcodec.h"
+#include "internal.h"
 #include "libavutil/avstring.h"
 #include "libavutil/opt.h"
 

libavcodec/libspeexdec.c

@@ -23,6 +23,7 @@
 #include <speex/speex_stereo.h>
 #include <speex/speex_callbacks.h>
 #include "avcodec.h"
+#include "internal.h"
 
 typedef struct {
     AVFrame frame;