atl1: fix transmit timeout bug

See http://marc.info/?l=linux-netdev&m=121931988219314&w=2

Stop the queue and turn off carrier to prevent transmit timeouts
when the cable is unplugged/replugged.

Signed-off-by: Jay Cliburn <jacliburn@bellsouth.net>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>