net/enic: add missing Tx offload flags

net/enic: add missing Tx offload flags

The following commit has added a number of existing offload flags such
as PKT_TX_IPV4 and PKT_TX_IPV6 to PKT_TX_OFFLOAD_MASK defined in
rte_mbuf.h. That change breaks the enic driver's Tx prepare handler.

commit ef28cfa73822 ("mbuf: fix Tx offload mask")

The enic driver keeps the supported offload flags in a local variable
(tx_offload_mask), which is strictly a subset of
PKT_TX_OFFLOAD_MASK. This variable is then used to compute the
unsupported flags (tx_offload_notsup_mask), and the Tx prepare handler
(tx_pkt_prepare) uses it to reject packets with unsupported offload
flags.

As is, tx_offload_notsup_mask ends up containing flags like
PKT_TX_IPV4 that are actually supported by the driver, which then
breaks any application that uses checksum offloads and calls the Tx
prepare handler. So add the flags to tx_offload_mask that the driver
supports but were missing in PKT_TX_OFFLOAD_MASK.

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