The number of Linux kernel related config options has become quite big
over the past few months, they deserve their own Config-kernel.in file.

Signed-off-by: Florian Fainelli <florian@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38524 3c298f89-4303-0410-b956-a3cf2f4a3e73