selftests/bpf: Fix two minor compilation warnings reported by GCC 4.9

GCC 4.9 seems to be more strict in some regards. Fix two minor issue it
reported.

Fixes: 1c1052e ("tools/testing/selftests/bpf: Add self-tests for new helper bpf_get_ns_current_pid_tgid.")
Fixes: 2d7824f ("selftests: bpf: Add test for sk_assign")
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200820061411.1755905-3-andriin@fb.com

tools/testing/selftests/bpf/prog_tests/sk_assign.c

@@ -268,6 +268,7 @@ void test_sk_assign(void)
 	int server = -1;
 	int server_map;
 	int self_net;
+	int i;
 
 	self_net = open(NS_SELF, O_RDONLY);
 	if (CHECK_FAIL(self_net < 0)) {
@@ -286,7 +287,7 @@ void test_sk_assign(void)
 		goto cleanup;
 	}
 
-	for (int i = 0; i < ARRAY_SIZE(tests) && !READ_ONCE(stop); i++) {
+	for (i = 0; i < ARRAY_SIZE(tests) && !READ_ONCE(stop); i++) {
 		struct test_sk_cfg *test = &tests[i];
 		const struct sockaddr *addr;
 		const int zero = 0;

tools/testing/selftests/bpf/test_current_pid_tgid_new_ns.c

@@ -156,4 +156,5 @@ int main(int argc, char **argv)
 			bpf_object__close(obj);
 		}
 	}
+	return 0;
 }