This patch enables configurable tx_first burst number.
Use "start tx_first (burst_num)" to specify how many bursts of packets to
be sent before forwarding start, or "start tx_first" like before for the
default 1 burst send.
Signed-off-by: Zhihong Wang <zhihong.wang@intel.com>
Acked-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>