kunit: qemu_configs: Add LoongArch config

Add a basic config to run kunit tests on LoongArch.
This requires QEMU 9.1.0 or later for the necessary direct kernel boot
support.

Link: https://lore.kernel.org/r/20241111-kunit-loongarch-v2-1-7676eb5f2da3@linutronix.de


Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>