kernel-devsrc: add selinux include files needed by scripts/selinux build

If CONFIG_SECURITY_SELINUX=y is enabled in kernel configuration, then
'make scripts' command in /usr/src/kernel fails to build
utilities under scripts/selinux that would be pulled in by this config:

  HOSTCC  scripts/selinux/genheaders/genheaders
scripts/selinux/genheaders/genheaders.c:19:10: fatal error: classmap.h: No such file or directory
 #include "classmap.h"

To address this issue add security/selinux/include files into
kernel-devsrc.

(From OE-Core rev: 8dce789ae1a2c11521ebe895fd3bd636cff64261)

Signed-off-by: Victor Kamensky <kamensky@cisco.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-kernel/linux/kernel-devsrc.bb

@@ -210,6 +210,9 @@ do_install() {
 	    cp -a --parents kernel/bounds.c $kerneldir/build
 	    cp -a --parents Kbuild $kerneldir/build
 	fi
+
+        # required to build scripts/selinux/genheaders/genheaders
+        cp -a --parents security/selinux/include/* $kerneldir/build/
     )
 
     # Make sure the Makefile and version.h have a matching timestamp so that