net: dpaa2-eth: use dev_close/open instead of the internal functions

Instead of calling the internal functions which implement .ndo_stop and
.ndo_open, we can simply call dev_close and dev_open, so that we keep
the code cleaner.

Also, in the next patches we'll use the same APIs from other files
without needing to export the internal functions.

Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>