wasapi2device: Make wasapi2 device distinguishable from wasapi device
Both wasapi2 and wasapi plugins use WASAPI API. So "device.api=wasapi" would make sense for the wasapi2 plugin as well. But people would be confused by the identical "device.api=wasapi" property if intended plugin is wasapi, not wasapi2. This change will make them distinguishable by using "device.api" device property.