de2104x: fix power management

At least my 21041 cards come out of suspend with bus mastering disabled so
they did not work after resume(no data transferred).
After adding pci_set_master(), the driver oopsed immediately on resume -
because de_clean_rings() is called on suspend but de_init_rings() call
was missing in resume.

Also disable link (reset SIA) before sleep (de4x5 does this too).

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Acked-by: Jeff Garzik <jgarzik@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>