Add support for regulation to WiFi driver

[jerome-pouiller]

Need to implement:

/** Set or get regulatory domain
 *
 * @param dev Pointer to the device structure for the driver instance.
 * @param reg_domain Regulatory domain
 *
 * @return 0 if ok, < 0 if error
 */
int (*reg_domain)(const struct device *dev, struct wifi_reg_domain *reg_domain);