Revert "v4l2: check if kernel headers are recent enough"

This reverts commit 5740099f.
This caused autoconf errors and besides I still do not agree.

configure.ac

@@ -1809,18 +1809,7 @@ AC_ARG_ENABLE(pvr, [AS_HELP_STRING([--enable-pvr],
   [support PVR V4L2 cards (default disabled)])])
 have_v4l2="no"
 AC_CHECK_HEADERS([linux/videodev2.h sys/videoio.h], [
-  AC_PREPROC_IFELSE([
-  #ifdef __linux__
-  # include <linux/version.h>
-  # if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,32)
-  #  error Kernel headers too old
-  # endif
-  #endif
-    ], [
   have_v4l2="yes"
-      ], [
-      AC_MSG_WARN([Kernel headers too old for V4L2 module. You need at least 2.6.32])
-  ])
 ])
 AS_IF([test "$have_v4l2" = "yes"], [
   AS_IF([test "${enable_libv4l2}" != "no"], [