There are several valid extensions that kernel modules can have, and the
list I had here was not complete... this meant that mkinitfs would fail
to include modules with extensions like ".ko.gz" when searching
directories.
This makes the check for a "valid" module file name a lot simpler,
allowing any file with ".ko" in the file name. While it's possible for a
non-module file to have ".ko" somewhere in the file name, it seems
unlikely if it's in the kernel modules directory... and this is an OK
compromise for now.
e2f4e6254f