kunit: tool: Add support for m68k under QEMU

Add basic support to run m68k under QEMU via kunit_tool.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>