perf lock: Carefully combine lock stats for discarded entries

Stats from discarded entries should be omitted.

But a lock class may have both good and bad entries.

If the first entry was bad, we can zero-fill the stats and only add good
stats if any.

The entry can remove the discard state if it finds a good entry later.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220127000050.3011493-7-namhyung@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>