net: enetc: remove unneeded xdp_do_flush_map()

xdp_do_redirect already contains:
-> dev_map_enqueue
   -> __xdp_enqueue
      -> bq_enqueue
         -> bq_xmit_all // if we have more than 16 frames

So the logic from enetc will never be hit, because ENETC_DEFAULT_TX_WORK
is 128.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>