netxen: fix tx timeout recovery

Redesign tx timeout handling in line with new firmware
reset design that co-ordinates with other PCI function
drivers.

o For NX3031, first try to reset PCI function's own
  context before requesting firmware reset.

o For NX2031, since firmware heartbit is not supported
  directly request firmware reset.

Signed-off-by: Amit Kumar Salecha <amit@netxen.com>
Signed-off-by: Dhananjay Phadke <dhananjay@netxen.com>
Signed-off-by: David S. Miller <davem@davemloft.net>