selftests: net: use the dummy bpf from net/lib

selftests: net: use the dummy bpf from net/lib

Commit 29b036be1b0b ("selftests: drv-net: test XDP, HDS auto and
the ioctl path") added an sample XDP_PASS prog in net/lib, so
that we can reuse it in various sub-directories. Delete the old
sample and use the one from the lib in existing tests.

Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20250327222315.1098596-3-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>