simplify video4linux2 test

Originally committed as revision 7908 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -1775,14 +1775,7 @@ int main( void ) {
 }
 EOF
 
-# check for video4linux2 --- V4L2_PIX_FMT_YUV420
-enabled video4linux2 && check_cc <<EOF || video4linux2="no"
-#include <sys/time.h>
-#include <asm/types.h>
-#include <linux/videodev2.h>
-int dummy = V4L2_PIX_FMT_YUV420;
-struct v4l2_buffer dummy1;
-EOF
+enabled video4linux2 && check_header linux/videodev2.h || disable video4linux2
 
 # check for ioctl_meteor.h, ioctl_bt848.h and alternatives
 if enabled bktr; then