rtla: Add trace_instance_stop

Support not only turning trace on for the timerlat tracer, but also
turning it off.

This will be used in subsequent patches to stop the timerlat tracer
without also wiping the trace buffer.

Cc: stable@vger.kernel.org
Cc: John Kacur <jkacur@redhat.com>
Cc: Luis Goncalves <lgoncalv@redhat.com>
Cc: Gabriele Monaco <gmonaco@redhat.com>
Link: https://lore.kernel.org/20250116144931.649593-2-tglozar@redhat.com


Signed-off-by: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>