hw/usb/canokey: change license to GPLv2+

hw/usb/canokey: change license to GPLv2+

Apache license is considered by some to be not compatible
with GPLv2+. Since QEMU as combined work is GPLv2-only,
these two files should be made compatible.

Reported-by: "Daniel P. Berrangé" <berrange@redhat.com>
Link: https://lore.kernel.org/qemu-devel/ZEpKXncC%2Fe6FKRe9@redhat.com/
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Acked-By: canokeys.org (http://canokeys.org) <contact@canokeys.org>
Acked-by: YuanYang Meng <mkfssion@mkfssion.com>
Signed-off-by: Hongren (Zenithal) Zheng <i@zenithal.me>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>