Staging: batman-adv: Don't call free_netdev twice

Free_netdev is registered as destructor in interface_setup for every
soft_device. This destructor is automatically called from
unregister_netdev and we must not call it again for the freed
net_device.
Signed-off-by: Sven Eckelmann <sven.eckelmann@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/batman-adv/main.c

@@ -128,6 +128,9 @@ int init_module(void)
 
 unreg_soft_device:
 	unregister_netdev(soft_device);
+	soft_device = NULL;
+	return -ENOMEM;
+
 free_soft_device:
 	free_netdev(soft_device);
 	soft_device = NULL;