tulip: Fix dead 21041 ethernet after ifconfig down

The de2104x did a pci_disable_device() in it's close function, but
the open function never does a pci_enable_device() and assumes that
the device is already enabled. Considering that downing the interface
is just a temporary thing the pci_disable_device() isn't a pretty good
idea and removing it from the close function just fixes the bug.

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Acked-by: Grant Grundler <grundler@parisc-linux.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>