kunit: tool: Add support for SH under QEMU

Add basic support to run SH under QEMU via kunit_tool using the
virtualized r2d platform.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>