dp83640: free packet queues on remove

If the PHY should disappear (for example, on an USB Ethernet MAC), then
the driver would leak any undelivered time stamp packets. This commit
fixes the issue by calling the appropriate functions to free any packets
left in the transmit and receive queues.

The driver first appeared in v3.0.

Signed-off-by: Richard Cochran <richard.cochran@omicron.at>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>