FROMLIST: tracing: add trace_export support for trace_marker

Add the support to route trace_marker buffer to other destination
via trace_export.

Bug: 160464759
Link: https://lore.kernel.org/patchwork/cover/1280618/


Signed-off-by: Tingwei Zhang <tingwei@codeaurora.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Change-Id: I870f1902e48d05947667ac0ecda7a9d17a982890