ixgbe: unify Rx setup

ixgbe: unify Rx setup

   - Set the callback in a single function that is called from
     ixgbe_dev_rx_init() for a primary process and from eth_ixgbe_dev_init()
     for a secondary processes. This is instead of multiple, hard to track places.
   - Added ixgbe_hw.rx_bulk_alloc_allowed - see ixgbe_hw.rx_vec_allowed description below.
   - Added ixgbe_hw.rx_vec_allowed: like with Bulk Allocation, Vector Rx is
     enabled or disabled on a per-port level. All queues have to meet the appropriate
     preconditions and if any of them doesn't - the feature has to be disabled.
     Therefore ixgbe_hw.rx_vec_allowed will be updated during each queues configuration
     (rte_eth_rx_queue_setup()) and then used in rte_eth_dev_start() to configure the
     appropriate callbacks. The same happens with ixgbe_hw.rx_vec_allowed in a Bulk Allocation
     context.
   - Bugs fixed:
      - Vector scattered packets callback was called regardless the appropriate
        preconditions:
         - Vector Rx specific preconditions.
         - Bulk Allocation preconditions.
      - Vector Rx was enabled/disabled according to the last queue setting and not
        based on all queues setting (which may be different for each queue).

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