modules: fix issue with some module extensions being ignored in dirs (MR 46)

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.

internal/filelist/modules/modules.go

@@ -118,7 +118,9 @@ func getModulesInDir(modPath string) (files []string, err error) {
 			// Unable to walk path
 			return err
 		}
-		if filepath.Ext(path) != ".ko" && filepath.Ext(path) != ".xz" {
+		// this assumes module names are in the format <name>.ko[.format],
+		// where ".format" (e.g. ".gz") is optional.
+		if !strings.Contains(".ko", path) {
 			return nil
 		}
 		files = append(files, path)