selftests/bpf: fix a compilation error

I hit the following compilation error with gcc 4.8.5.

prog_tests/flow_dissector.c: In function ‘test_flow_dissector’:
prog_tests/flow_dissector.c:155:2: error: ‘for’ loop initial declarations are only allowed in C99 mode
for (int i = 0; i < ARRAY_SIZE(tests); i++) {
^
prog_tests/flow_dissector.c:155:2: note: use option -std=c99 or -std=gnu99 to compile your code

Let us fix the issue by avoiding this particular c99 feature.

Fixes: a5cb33464e53 ("selftests/bpf: make flow dissector tests more extensible")
Signed-off-by: Yonghong Song <[e-mail]>
Signed-off-by: Alexei Starovoitov <[e-mail]>

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

···
 void test_flow_dissector(void)
 {
 	struct bpf_object *obj;
-	int err, prog_fd;
+	int i, err, prog_fd;
 
 	err = bpf_flow_load(&obj, "./bpf_flow.o", "flow_dissector",
 			    "jmp_table", &prog_fd);
···
 		return;
 	}
 
-	for (int i = 0; i < ARRAY_SIZE(tests); i++) {
+	for (i = 0; i < ARRAY_SIZE(tests); i++) {
 		struct bpf_flow_keys flow_keys;
 		struct bpf_prog_test_run_attr tattr = {
 			.prog_fd = prog_fd,