selftests/net: enable io_uring sendzc testing

d8b6171 ("selftests/io_uring: test zerocopy send") added io_uring
zerocopy tests but forgot to enable it in make runs. Add missing
io_uring_zerocopy_tx.sh into TEST_PROGS.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/28e743602cdd54ffc49f68bbcbcbafc59ba22dc2.1664142210.git.asml.silence@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/Makefile

@@ -66,6 +66,7 @@ TEST_GEN_FILES += cmsg_sender
 TEST_GEN_FILES += stress_reuseport_listen
 TEST_PROGS += test_vxlan_vnifiltering.sh
 TEST_GEN_FILES += io_uring_zerocopy_tx
+TEST_PROGS += io_uring_zerocopy_tx.sh
 TEST_GEN_FILES += bind_bhash
 TEST_GEN_PROGS += sk_bind_sendto_listen
 TEST_GEN_PROGS += sk_connect_zero_addr