tests: Update check-clean rule

Only i386, x86_64, sparc and sparc64 qtests were cleaned up.
Make this more generic to not miss any newly tested targets.

Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Andreas Färber <afaerber@suse.de>
