sky2: Yukon Extreme support

This is basic support for the new Yukon Extreme
chip, extracted from the new vendor driver 10.0.4.3.

Since this is untested hardware, it has a big fat warning for now.

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