perf tools: Add stat config event read function

perf tools: Add stat config event read function

Introducing the perf_event__read_stat_config function to read a struct
perf_stat_config object data from a stat config event.

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]>