selftests/bpf: Turn fexit_bpf2bpf into test with subtests

There are clearly 4 subtests, so make it official.

Signed-off-by: Andrii Nakryiko <[e-mail]>
Signed-off-by: Alexei Starovoitov <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c

···
 
 void test_fexit_bpf2bpf(void)
 {
-	test_target_no_callees();
-	test_target_yes_callees();
-	test_func_replace();
-	test_func_replace_verify();
-	test_func_sockmap_update();
-	test_func_replace_return_code();
-	test_func_map_prog_compatibility();
+	if (test__start_subtest("target_no_callees"))
+		test_target_no_callees();
+	if (test__start_subtest("target_yes_callees"))
+		test_target_yes_callees();
+	if (test__start_subtest("func_replace"))
+		test_func_replace();
+	if (test__start_subtest("func_replace_verify"))
+		test_func_replace_verify();
+	if (test__start_subtest("func_sockmap_update"))
+		test_func_sockmap_update();
+	if (test__start_subtest("func_replace_return_code"))
+		test_func_replace_return_code();
+	if (test__start_subtest("func_map_prog_compatibility"))
+		test_func_map_prog_compatibility();
 }