net/pcap: fix Tx return count in error conditions

net/pcap: fix Tx return count in error conditions

When a packet cannot be transmitted, the driver is supposed to free this
packet and report it as handled.
This is to prevent the application from retrying to send the same packet
and ending up in a liveloop since the driver will never manage to send
it.

Fixes: 49a0a2ffd5db ("net/pcap: fix possible mbuf double freeing")
Fixes: 6db141c91e1f ("pcap: support jumbo frames")
Cc: stable@dpdk.org
Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>