acinclude.m4: Support Linux kernel 4.12

Allow datapath kernel modules to be configured and built for kernels up
to 4.12.

Signed-off-by: Greg Rose <gvrose8192@gmail.com>
Signed-off-by: Joe Stringer <joe@ovn.org>

acinclude.m4

@@ -143,7 +143,7 @@ AC_DEFUN([OVS_CHECK_LINUX], [
     AC_MSG_RESULT([$kversion])
 
     if test "$version" -ge 4; then
-       if test "$version" = 4 && test "$patchlevel" -le 11; then
+       if test "$version" = 4 && test "$patchlevel" -le 12; then
           : # Linux 4.x
        else
           AC_ERROR([Linux kernel in $KBUILD is version $kversion, but version newer than 4.11.x is not supported (please refer to the FAQ for advice)])