selftests, bpf: xdping is not meant to be run standalone

The actual test to run is test_xdping.sh, which is already in TEST_PROGS.
The xdping program alone is not runnable with 'make run_tests', it
immediatelly fails due to missing arguments.

Move xdping to TEST_GEN_PROGS_EXTENDED in order to be built but not run.

Fixes: cd538502 ("selftests/bpf: measure RTT from xdp using xdping")
Signed-off-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/4365c81198f62521344c2215909634407184387e.1573821726.git.jbenc@redhat.com

tools/testing/selftests/bpf/Makefile

@@ -30,7 +30,7 @@ TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test
 	test_sock test_btf test_sockmap get_cgroup_id_user test_socket_cookie \
 	test_cgroup_storage test_select_reuseport \
 	test_netcnt test_tcpnotify_user test_sock_fields test_sysctl test_hashmap \
-	test_cgroup_attach xdping test_progs-no_alu32
+	test_cgroup_attach test_progs-no_alu32
 
 # Also test bpf-gcc, if present
 ifneq ($(BPF_GCC),)
@@ -71,7 +71,7 @@ TEST_PROGS_EXTENDED := with_addr.sh \
 # Compile but not part of 'make run_tests'
 TEST_GEN_PROGS_EXTENDED = test_sock_addr test_skb_cgroup_id_user \
 	flow_dissector_load test_flow_dissector test_tcp_check_syncookie_user \
-	test_lirc_mode2_user
+	test_lirc_mode2_user xdping
 
 TEST_CUSTOM_PROGS = urandom_read