ionic: add queue lock around open and stop

Add the queue configuration lock to ionic_open() and
ionic_stop() so that they don't collide with other in parallel
queue configuration actions such as MTU changes as can be
demonstrated with a tight loop of ifup/change-mtu/ifdown.

Signed-off-by: Shannon Nelson <snelson@pensando.io>
Signed-off-by: David S. Miller <davem@davemloft.net>