perf evsel: Add a backpointer to the evlist a evsel is in

perf evsel: Add a backpointer to the evlist a evsel is in

So that functions that deal primarily with an evsel to access
information that concerns the whole evlist it is in.

Cc: Adrian Hunter <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Kan Liang <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>