dp83640: Make use of skb_queue_purge instead of reimplementing the code

This change makes it so that dp83640_remove can use skb_queue_purge
instead of looping through itself to flush any entries out of the queue.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>