lib: use KSTM_MODULE_GLOBALS macro in kselftest drivers

Instead of defining the total/failed test counters manually,
test drivers that are clients of kselftest should use the
macro created for this purpose.

Signed-off-by: Timur Tabi <timur@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210214161348.369023-2-timur@kernel.org