samsung-laptop: remove selftest

We can now do the self test using debugfs, so remove the code
and keep the debug flag to enable more traces.

Signed-off-by: Corentin Chary <corentincj@iksaif.net>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Matthew Garrett <mjg@redhat.com>