qede: Free netdevice only after stoping slowpath

qed needs to be informed of the removal of the qede interface
prior to its actual removal, as qede has some registered callbacks
that might get called async to the removal flow.

Signed-off-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>