libqmi-glib: make 'QmiCtlDataLinkProtocol' a enum instead of flags
libqmi-glib: make 'QmiCtlDataLinkProtocol' a enum instead of flags

If the values are like flags, but mutually exclusive, just set it as an enum.

roland-wilhelm/libqmi,roland-wilhelm/libqmi,roland-wilhelm/libqmi,roland-wilhelm/libqmi