selftests/bpf: add wrapper scripts for test_xdp_vlan.sh

In-order to test both native-XDP (xdpdrv) and generic-XDP (xdpgeneric)
create two wrapper test scripts, that start the test_xdp_vlan.sh script
with these modes.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>