selftests/bpf: less spam in the log for message matching

When running test_loader based tests in the verbose mode each matched
message leaves a trace in the stderr, e.g.:

    ./test_progs -vvv -t ...
    validate_msgs:PASS:expect_msg 0 nsec
    validate_msgs:PASS:expect_msg 0 nsec
    validate_msgs:PASS:expect_msg 0 nsec
    validate_msgs:PASS:expect_msg 0 nsec
    validate_msgs:PASS:expect_msg 0 nsec

This is not very helpful when debugging such tests and clobbers the
log a lot.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20240820102357.3372779-2-eddyz87@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/test_loader.c

@@ -531,7 +531,8 @@ static void validate_msgs(char *log_buf, struct expected_msgs *msgs,
 			}
 		}
 
-		if (!ASSERT_OK_PTR(match, "expect_msg")) {
+		if (!match) {
+			PRINT_FAIL("expect_msg\n");
 			if (env.verbosity == VERBOSE_NONE)
 				emit_fn(log_buf, true /*force*/);
 			for (j = 0; j <= i; j++) {