selftests: bpf: update .gitignore with missing generated files

Signed-off-by: NAnders Roxell <anders.roxell@linaro.org>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

tools/testing/selftests/bpf/.gitignore

@@ -12,3 +12,6 @@ test_tcpbpf_user
 test_verifier_log
 feature
 test_libbpf_open
+test_sock
+test_sock_addr
+urandom_read