examples/vhost: fix header copy to discontiguous desc buffer
examples/vhost: fix header copy to discontiguous desc buffer

In the loop to copy virtio-net header to the descriptor buffer,
destination pointer was incremented instead of the source
pointer.

Coverity issue: 277240
Fixes: 82c93a567d3b ("examples/vhost: move to safe GPA translation API")

Signed-off-by: Maxime Coquelin <9a2667dee3b90866bbc9c2696cff2b7d5616c95a@redhat.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk