ixgbe: add LRO support

ixgbe: add LRO support

    - Only x540 and 82599 devices support LRO.
    - Add the appropriate HW configuration.
    - Add RSC aware rx_pkt_burst() handlers:
       - Implemented bulk allocation and non-bulk allocation versions.
       - Add LRO-specific fields to rte_eth_rxmode, to rte_eth_dev_data
         and to ixgbe_rx_queue.
       - Use the appropriate handler when LRO is requested.

Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>