net/virtio: fix xstats name

net/virtio: fix xstats name

We have a stats named "size_1024_1517_packets", while the code
actually counts the range "[1024, 1518]", which is obviously wrong.
The code is as follows in the function virtio_update_packet_stats.

else if (s < 1519)
		stats->size_bins[6]++;

We could either fix it by correcting the "if" check in the code,
or fix it by just renaming the stats to conform to the code. The
latter solution is taken because that's what the RFC2819 suggests.

Fixes: 76d4c652e07d ("virtio: add extended stats")

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