Optimise usage of videodev2.h header

http/http_h264.c

@@ -52,7 +52,7 @@ bool h264_is_key_frame(buffer_t *buf)
 {
   unsigned char *data = buf->start;
 
-  if (buf->v4l2.flags & V4L2_BUF_FLAG_KEYFRAME) {
+  if (buf->flags.is_keyframe) {
     E_LOG_DEBUG(buf, "Got key frame (from V4L2)!");
     return true;
   } else if (buf->used >= 5 && (data[4] & 0x1F) == 0x07) {