selftests: drv-net: Test XDP_TX support

selftests: drv-net: Test XDP_TX support

Add test to verify the XDP_TX functionality by generating traffic from a
remote node on a specific UDP port and redirecting it back to the sender.

./drivers/net/xdp.py
TAP version 13
1..5
ok 1 xdp.test_xdp_native_pass_sb
ok 2 xdp.test_xdp_native_pass_mb
ok 3 xdp.test_xdp_native_drop_sb
ok 4 xdp.test_xdp_native_drop_mb
ok 5 xdp.test_xdp_native_tx_mb
\# Totals: pass:5 fail:0 xfail:0 xpass:0 skip:0 error:0

Signed-off-by: Mohsin Bashir <mohsin.bashr@gmail.com>
Link: https://patch.msgid.link/20250719083059.3209169-4-mohsin.bashr@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>