selftests: drv-net: xdp: add test for interface level qstats

selftests: drv-net: xdp: add test for interface level qstats

Send a non-trivial number of packets and make sure that they
are counted correctly in qstats. Per qstats specification
XDP is the first layer of the stack so we should see Rx and Tx
counters go up for packets which went thru XDP.

Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20251007232653.2099376-6-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>