Sun GEM ethernet: enable and map PCI ROM properly

This same patch was reported to fix the MAC address detection on sunhme
(next patch).  Most people seem to be running this on Sparcs or PPC
machines, where we get the MAC address from their respective firmware
rather than from the (previously broken) ROM mapping routines.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>