sky2: dual port NAPI problem

Shutting down port 0 disables the NAPI poll used by both ports.
The long term fix will be to separate NAPI object from net device
until then just reenable if needed.

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