sky2: cleanup restart operations

This unifies the places that bounce the device (suspend/resume
and restart). And makes the operations have the same semantics
as normal dev_open/dev_stop.

This also avoids setting the multicast addresses twice when
device is brought up.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>