An #ifdef for the kernel version was missing around the header of
debugfs_create_devm_seqfile() and the LINUX_BACKPORT() was also not
done.

This closes #20181

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>


git-svn-id: svn://svn.openwrt.org/openwrt/trunk@46492 3c298f89-4303-0410-b956-a3cf2f4a3e73