seltests: bpf: test_tunnel: Use ip neigh

The 'arp' command is deprecated and is another dependency of the selftest.
Just use 'ip neigh', the test depends on iproute2 already.
Signed-off-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/40f24b9d3f0f53b5c44471b452f9a11f4d13b7af.1632236133.git.jbenc@redhat.com

tools/testing/selftests/bpf/test_tunnel.sh

@@ -168,14 +168,15 @@ add_vxlan_tunnel()
 	ip netns exec at_ns0 \
 		ip link set dev $DEV_NS address 52:54:00:d9:01:00 up
 	ip netns exec at_ns0 ip addr add dev $DEV_NS 10.1.1.100/24
-	ip netns exec at_ns0 arp -s 10.1.1.200 52:54:00:d9:02:00
+	ip netns exec at_ns0 \
+		ip neigh add 10.1.1.200 lladdr 52:54:00:d9:02:00 dev $DEV_NS
 	ip netns exec at_ns0 iptables -A OUTPUT -j MARK --set-mark 0x800FF
 
 	# root namespace
 	ip link add dev $DEV type $TYPE external gbp dstport 4789
 	ip link set dev $DEV address 52:54:00:d9:02:00 up
 	ip addr add dev $DEV 10.1.1.200/24
-	arp -s 10.1.1.100 52:54:00:d9:01:00
+	ip neigh add 10.1.1.100 lladdr 52:54:00:d9:01:00 dev $DEV
 }
 
 add_ip6vxlan_tunnel()