avcodec/v4l2_m2m: add missing header inclusions

Should fix checkheaders on systems where v4l2_m2m is enabled.
Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/v4l2_buffers.h

@@ -24,6 +24,8 @@
 #ifndef AVCODEC_V4L2_BUFFERS_H
 #define AVCODEC_V4L2_BUFFERS_H
 
+#include <linux/videodev2.h>
+
 enum V4L2Buffer_status {
     V4L2BUF_AVAILABLE,
     V4L2BUF_IN_DRIVER,

libavcodec/v4l2_context.h

@@ -25,6 +25,8 @@
 #define AVCODEC_V4L2_CONTEXT_H
 
 #include <stdatomic.h>
+#include <linux/videodev2.h>
+
 #include "libavcodec/avcodec.h"
 #include "libavutil/pixfmt.h"
 #include "libavutil/frame.h"

libavcodec/v4l2_m2m.h

@@ -27,6 +27,8 @@
 #include <semaphore.h>
 #include <unistd.h>
 #include <dirent.h>
+#include <linux/videodev2.h>
+
 #include "libavcodec/avcodec.h"
 #include "v4l2_context.h"