selftests: net: use TEST_PROGS_EXTENDED

When a script file that isn't generated uses the variable
TEST_GEN_PROGS_EXTENDED and a 'make -C tools/testing/selftests clean' is
performed the script file gets removed and git shows the file as
deleted. For script files that isn't generated TEST_PROGS_EXTENDED
should be used.

Fixes: 9faedd643fd9 ("selftests: net: add in_netns.sh TEST_GEN_PROGS_EXTENDED")
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/net/Makefile

@@ -6,7 +6,7 @@ CFLAGS += -I../../../../usr/include/
 
 TEST_PROGS := run_netsocktests run_afpackettests test_bpf.sh netdevice.sh rtnetlink.sh
 TEST_PROGS += fib_tests.sh fib-onlink-tests.sh pmtu.sh
-TEST_GEN_PROGS_EXTENDED := in_netns.sh
+TEST_PROGS_EXTENDED := in_netns.sh
 TEST_GEN_FILES =  socket
 TEST_GEN_FILES += psock_fanout psock_tpacket msg_zerocopy
 TEST_GEN_PROGS = reuseport_bpf reuseport_bpf_cpu reuseport_bpf_numa