ixgbe: set default Rx/Tx configuration
ixgbe: set default Rx/Tx configuration

Many sample apps use duplicated code to set rte_eth_txconf and rte_eth_rxconf
structures. This patch allows the user to get a default optimal RX/TX configuration
through rte_eth_dev_info get, and still any parameters may be tweaked as wished,
before setting up queues.

Signed-off-by: Pablo de Lara <28355d9cfe41bb8148aea0fb24f47aae8f4217a1@intel.com>
Reviewed-by: Bruce Richardson <66b9e8e8fbd5e9f41f91b0af050876182ce9d0e4@intel.com>
Acked-by: David Marchand <f28529695cfa9e3e1eb84e7072aa626af4abb18e@6wind.com>
[Thomas: split patch]

phermansson/dpdk,phermansson/dpdk,phermansson/dpdk,phermansson/dpdk