trace-cmd: upgraded package to upstream

Upgraded dev-util/trace-cmd to version 2.9.1.

To pick up this, for one:

  https://git.kernel.org/pub/scm/linux/kernel/git/rostedt/trace-cmd.git/commit/?id=5502bcef0f962cda73f6fd86d5742711b8094b1a
  trace-cmd: Handle filtered PIDs per ftarce instance

The '-c' option will follow children for both trace events and for
ftrace now.

BUG=none
TEST=run it, e.g., to ftrace powerd and its subprocesses:
     `trace-cmd record -p function -l '*' -P $(pidof powerd) -c`

Change-Id: Ie7ae599a4493f0dafeb2ed5741ad92779256cb08
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2490229
Tested-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
Commit-Queue: Brian Norris <briannorris@chromium.org>