perf tools: Add event_update user level event

perf tools: Add event_update user level event

It'll serve as a base event for additional event attributes details,
that are not part of the attr event.

At the moment this event is just a dummy one without any specific
functionality. The type value will distinguish the update event details.
It'll come in the following patches.

The idea for this event is to be extensible for any update that the
event might need in the future.

Signed-off-by: Jiri Olsa <[email protected]>
Tested-by: Kan Liang <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>