rtla/timerlat_top: Set OSNOISE_WORKLOAD for kernel threads

When using rtla timerlat with userspace threads (-u or -U), rtla
disables the OSNOISE_WORKLOAD option in
/sys/kernel/tracing/osnoise/options. This option is not re-enabled in a
subsequent run with kernel-space threads, leading to rtla collecting no
results if the previous run exited abnormally:

$ rtla timerlat top -u
^\Quit (core dumped)
$ rtla timerlat top -k -d 1s
                                     Timer Latency
  0 00:00:01   |          IRQ Timer Latency (us)        |         Thread Timer Latency (us)
CPU COUNT      |      cur       min       avg       max |      cur       min       avg       max

The issue persists until OSNOISE_WORKLOAD is set manually by running:
$ echo OSNOISE_WORKLOAD > /sys/kernel/tracing/osnoise/options

Set OSNOISE_WORKLOAD when running rtla with kernel-space threads if
available to fix the issue.

Cc: stable@vger.kernel.org
Cc: John Kacur <jkacur@redhat.com>
Cc: Luis Goncalves <lgoncalv@redhat.com>
Link: https://lore.kernel.org/20250107144823.239782-4-tglozar@redhat.com
Fixes: cdca4f4 ("rtla/timerlat_top: Add timerlat user-space support")
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

tools/tracing/rtla/src/timerlat_top.c

@@ -851,12 +851,15 @@ timerlat_top_apply_config(struct osnoise_tool *top, struct timerlat_top_params *
 		}
 	}
 
-	if (params->user_top) {
-		retval = osnoise_set_workload(top->context, 0);
-		if (retval) {
-			err_msg("Failed to set OSNOISE_WORKLOAD option\n");
-			goto out_err;
-		}
+	/*
+	* Set workload according to type of thread if the kernel supports it.
+	* On kernels without support, user threads will have already failed
+	* on missing timerlat_fd, and kernel threads do not need it.
+	*/
+	retval = osnoise_set_workload(top->context, params->kernel_workload);
+	if (retval < -1) {
+		err_msg("Failed to set OSNOISE_WORKLOAD option\n");
+		goto out_err;
 	}
 
 	if (isatty(STDOUT_FILENO) && !params->quiet)