kernel.bbclass: Add missing modules.order and modules.builtins

kernel.bbclass: Add missing modules.order and modules.builtins

When running depmod, from kmod, warnings about missing modules.order
and modules.builtins occur.  Looking back it is not clear why these
files were being ignored, other then nobody knew what to do with them.

Add the files into the kernel-base package, if they exist, ensuring
they will always get installed if at least one module is installed.

[ YOCTO #3963 ]

(From OE-Core rev: bff4bda1fe86ddd218a192a14605924205a5300b)

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>