target-finalize: avoid stripping kernel modules with incorrect permissions

If a kernel module is installed with incorrect permissions (0755 iso 0644),
it would get stripped in a way that would render the kernel module broken.
While the incorrect permissions are a developer error, it is a minor change
to prevent this mistake from causing incorrectly stripped modules.

This was reported with bug #6992:
https://bugs.busybox.net/show_bug.cgi?id=6992



Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>