This version fixes:
- missing rtnl_lock()/rtnl_unload() bug on unregister_hdlc_device
- N2, C101: interrupt handler now works under high IRQ load from other
  devices (with previous versions, the IRQ processing for the card could
  sometimes stop after reaching "work limit")

This is production-tested on devices I have access to (N2, C101, PC300,
PCI200SYN).