New field in hdlc_device: void *priv;
New helpers:
        struct net_device *alloc_hdlcdev(priv) allocates hdlc, sets ->priv and
returns pointer to hdlc->netdev
        free_hdlcdev(dev) takes such pointer and frees its hdlc.

wanxl switched to use of those; instead of embedding hdlc into card->ports[]
we allocate it separately right after card had been allocated and store pointer
to hdlc->netdev in card->ports[]->dev.  Freeing is done just before freeing
card.  Pointer back to card->ports[] is stored in hdlc->priv.  port_to_dev()
and dev_to_port() rewritten in the obvious way; by now the rest of driver
doesn't care whether hdlc is embedded or not - everything uses port_to_dev()
and dev_to_port().

That killed embedded hdlc replacing it with pointer to net_device.  Fairly
similar work will be done in the next few patches for other drivers.

Additionally, setup-after-register and free_irq()-before-unregister races
had been fixed.