dpaa_eth: extend delays in ndo_stop

Make sure all the frames that are in flight have time to be processed
before the interface is completely brought down. Add a missing delay
for the Rx path.

Signed-off-by: Madalin Bucur <madalin.bucur@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>