sky2: Yukon Extreme (88e8071) support.

Enable support for Yukon EX chipset (88e8071).
Most of changes are related to new commands to chip for transmit,
and change in status and checksumming.

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