sky2: re-enable 88E8056 for most motherboards

This fixes the regression in 2.6.21 for users with 88e8056 on motherboard.
Allow all but the Gigabyte motherboard has some unresolved bus problems.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>