netxen: support pci error handlers

o Support pci error detection and recovery.
o Refactor suspend and resume code, to share with io_error_detected,
  and slot_reset callbacks
o NX_NEED_AER device state added, to synchronize with firmware
  recovery.

Signed-off-by: Amit Kumar Salecha <amit.salecha@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>