core: enable Easytether Android USB interfaces

These interfaces are a proprietary USB-ethernet-style virtual interface
that of course does not have proper driver links.  Given that it's so
easy to support, just do it.

src/nm-udev-manager.c

@@ -385,9 +385,13 @@ device_creator (NMUdevManager *manager,
 	}
 
 	if (!driver) {
+                if (g_str_has_prefix (ifname), "easytether") {
+                        driver = "easytether";
+                } else {
 		        nm_log_warn (LOGD_HW, "%s: couldn't determine device driver; ignoring...", path);
 		        goto out;
                 }
+	}
 
 	ifindex = g_udev_device_get_sysfs_attr_as_int (udev_device, "ifindex");
 	if (ifindex <= 0) {