rfkill: set encoding as NULL
The default encoding for GIOChannel is UTF-8, but rfkill event is binary data. If the value is invalid UTF-8, gsd-rfkill-manager will fail to receive rfkill event.
The default encoding for GIOChannel is UTF-8, but rfkill event is binary data. If the value is invalid UTF-8, gsd-rfkill-manager will fail to receive rfkill event.