[BUG][2.5]deadlock on cpci hot insert

[Rusty Lynch <rusty@penguin.co.intel.com>]

When I hot insert a cpci peripheral board into a ZT5084 chassis
with a ZT5550 system master board, my ZT5550 locks up.  I managed
to isolate the problem to a deadlock with list_lock

* hot insert * 
      ||
      \/
cpci_hotplug_core.c:check_slots() which does a spin_lock(&list_lock)
      ||
      \/
* inserted card is found *
      ||
      \/
cpci_hotplug_pci.c:cpci_configure_slot()
      ||
      \/
pci_hotplug_util.c:pci_visit_dev()
      ||
      || (fn->visit_pci_dev)
      \/
cpci_hotplug_pci.c:configure_visit_pci_dev()
      ||
      \/
cpci_hotplug_core.c:cpci_find_slot() which also does a spin_lock(&list_lock)
      ||
      \/
* deadlock *


I'm not sure which is the correct way to fix this.  Maybe a
cpci_unlocked_find_slot()? hmm... pci_visit_dev is exported,
so anybody could call it.

    --rustyl