net/vhost: add extended statistics

net/vhost: add extended statistics

This feature adds vhost pmd extended statistics from per port perspective
in order to meet the requirements of the applications such as OVS etc.
RX/TX xstats count the bytes without CRC. This is different from physical
NIC stats with CRC.

The statistics counters are based on RFC 2819 and RFC 2863 as follows:

rx/tx_good_packets
rx/tx_total_bytes
rx/tx_missed_pkts
rx/tx_broadcast_packets
rx/tx_multicast_packets
rx/tx_unicast_packets
rx/tx_undersize_errors
rx/tx_size_64_packets
rx/tx_size_65_to_127_packets;
rx/tx_size_128_to_255_packets;
rx/tx_size_256_to_511_packets;
rx/tx_size_512_to_1023_packets;
rx/tx_size_1024_to_1522_packets;
rx/tx_1523_to_max_packets;
rx/tx_errors
rx_fragmented_errors
rx_jabber_errors
rx_unknown_protos_packets;

No API is changed or added.
rte_eth_xstats_get_names() to retrieve what kinds of vhost xstats are
supported,
rte_eth_xstats_get() to retrieve vhost extended statistics,
rte_eth_xstats_reset() to reset vhost extended statistics.

The usage of vhost pmd xstats is the same as virtio pmd xstats.
for example, when test-pmd application is running in interactive mode
vhost pmd xstats will support the two following commands:

show port xstats all | port_id will show vhost xstats
clear port xstats all | port_id will reset vhost xstats

net/virtio pmd xstats(the function virtio_update_packet_stats) is used
as reference when implementing the feature.

Tested-by: Ciara Loftus <ciara.loftus@intel.com>
Signed-off-by: Zhiyong Yang <zhiyong.yang@intel.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>