filter: new plugin whitelist logic

Several plugins define specific udev tags that must be available in
the device in order for the plugins to use them. Let's use these tags
as a direct indication that ModemManager can probe the devices.

In particular, this change would make all Ericsson MBM modems probed
right away also in STRICT filter mode, without needing to check the
ttyACM interface type or the available net ports.

src/mm-plugin.c

@@ -141,6 +141,12 @@ mm_plugin_get_name (MMPlugin *self)
     return self->priv->name;
 }
 
+const gchar **
+mm_plugin_get_allowed_udev_tags (MMPlugin *self)
+{
+    return (const gchar **) self->priv->udev_tags;
+}
+
 /*****************************************************************************/
 
 static gboolean