samples/bpf: xdp_monitor use err code from tracepoint xdp:xdp_devmap_xmit

Update xdp_monitor to use the recently added err code introduced
in tracepoint xdp:xdp_devmap_xmit, to show if the drop count is
caused by some driver general delivery problem.  Other kind of drops
will likely just be more normal TX space issues.

Signed-off-by: Jesper Dangaard Brouer <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
2 files changed