skge: Make sure both ports initialize correctly

If allocation of the second ports fails, make sure that hw->ports
 is not 2 otherwise we'll crash trying to access the second port.

This fix is copied from a similar fix in the sky2 driver (ca519274

...),
but is untested, as I don't have a skge card.

Signed-off-by: Mike McCormack <mikem@ring3k.org>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>