enic: support skb->xmit_more

Check and update posted_index only when skb->xmit_more is 0 or tx queue is full.

v2:
use txq_map instead of skb_get_queue_mapping(skb)

Signed-off-by: Govindarajulu Varadarajan <_govind@gmx.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc drivers/net/ethernet/cisco/enic/enic_main.c
Simple merge

diff --cc drivers/net/ethernet/cisco/enic/vnic_wq.h
Simple merge