Change the codes in vhost sample to test virtio offload feature.
These changes include,
1. add two test options: tx-csum and tso.
2. add virtio_tx_offload() function to test vhost TX offload feature
for VM to NIC case;
however, for VM to VM case, it doesn't need to call this function,
the reason is explained in patch 2.
Signed-off-by: Jijiang Liu <jijiang.liu@intel.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
9fd72e3cbd