sky2: missing chip name for Yukon Supreme

Any usage of sky2 on new Yukon Supreme would cause a NULL dereference.
The chip is very new, so the support is still untested; vendor has
not sent any eval hardware.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>