samples/pktgen: remove remaining old pktgen sample scripts

Since commit 0f06a678 ("samples: Add an IPv6 '-6' option to the
pktgen scripts") the newer pktgen_sampleXX script does show howto use
IPv6 with pktgen.

Thus, there is no longer a reason to keep the older sample scripts around.

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