perf ordered_events: Add private data member

perf ordered_events: Add private data member

We will need it in following patch, where we can't use the
container_of() trick to get the higher level object.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-vgs9aoek21v14o3obza586yy@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>