netxen: fix failure cases for fw hang recovery

Handle few corner cases in firmware hang detection and recovery:

o Don't mark device state as READY, till handshake with
  firmware is done.
o During probe, if start_firmware fails, restore reference
  count.
o Don't increment refernce count, if start_firmware fails
  during firmware reset.
o Clear __NX_RESETTING bit, incase of fatal error or tempeature
  reaches critical limit so that pci remove() doesn't poll on
  this bit.

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