cred: get rid of CONFIG_DEBUG_CREDENTIALS

This code is rarely (never?) enabled by distros, and it hasn't caught
anything in decades. Let's kill off this legacy debug code.

Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

selftests: hid: add vmtest.sh

Similar-ish in many points from the script in selftests/bpf, with a few
differences:
- relies on boot2container instead of a plain qemu image (meaning that
we can take any container in a registry as a base)
- runs in the hid selftest dir, and such uses the test program from there
- the working directory to store the config is in
tools/selftests/hid/results

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>