drivers/at86rf215: make at86rf215_blocking_send a DEFAULT_MODULE
drivers/at86rf215: make at86rf215_blocking_send a DEFAULT_MODULE

So it can be disabled.

miri64/RIOT,jasonatran/RIOT,kYc0o/RIOT,kaspar030/RIOT,ant9000/RIOT,jasonatran/RIOT,ant9000/RIOT,RIOT-OS/RIOT,ant9000/RIOT,kYc0o/RIOT,miri64/RIOT,kYc0o/RIOT,kYc0o/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,ant9000/RIOT,miri64/RIOT,kaspar030/RIOT,miri64/RIOT,RIOT-OS/RIOT,jasonatran/RIOT,miri64/RIOT,jasonatran/RIOT,kaspar030/RIOT,kYc0o/RIOT,kaspar030/RIOT,jasonatran/RIOT,ant9000/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT