net/enic: use the new ethdev offloads API

net/enic: use the new ethdev offloads API

The following commits deprecate the use of the offload bit fields
(e.g. header_split) in rte_eth_rxmode and txq_flags in rte_eth_txconf.

commit ce17eddefc20 ("ethdev: introduce Rx queue offloads API")
commit cba7f53b717d ("ethdev: introduce Tx queue offloads API")

For enic, the required changes are mechanical. Use the new 'offloads'
field in rxmode instead of the bit fields. And, no changes required
with respect to txq_flags, as enic does not use it at all.

Per-queue RX offload capabilities are not set, as all offloads are
per-port at the moment.

Signed-off-by: Hyong Youb Kim <hyonkim@cisco.com>
Reviewed-by: John Daley <johndale@cisco.com>