netxen: fix crashes during module unload

This patch fixes two problems during driver unload. The pci_disable_device()
call is before firmware reload, causing reads and writes across PCI bus after
disabling device. Second problem is the register window was wrong during
firmware reload

Signed-off by: Dhananjay Phadke <dhananjay@netxen.com>

Signed-off-by: Jeff Garzik <jeff@garzik.org>