perf stat: Fix compatibility behavior

Instead of failing on an unknown event, when new perf stat is run on
older kernels:

  $ ./perf stat true
  Error: open_counter returned with 22 (Invalid argument). /bin/dmesg
  may provide additional information.

  Fatal: Not all events could be opened.

Just ignore EINVAL and ENOSYS, we'll print the results as not counted:

 Performance counter stats for 'true':

          0.239483 task-clock               #    0.493 CPUs utilized
                 0 context-switches         #    0.000 M/sec
                 0 CPU-migrations           #    0.000 M/sec
                86 page-faults              #    0.359 M/sec
           704,766 cycles                   #    2.943 GHz
     <not counted> stalled-cycles
           381,961 instructions             #    0.54  insns per cycle
            69,626 branches                 #  290.735 M/sec
             4,594 branch-misses            #    6.60% of all branches

        0.000485883  seconds time elapsed

Cc: Peter Zijlstra <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

tools/perf/builtin-stat.c

@@ -372,7 +372,10 @@ static int run_perf_stat(int argc __used, const char **argv)
 
 	list_for_each_entry(counter, &evsel_list->entries, node) {
 		if (create_perf_stat_counter(counter) < 0) {
-			if (errno == -EPERM || errno == -EACCES) {
+			if (errno == EINVAL || errno == ENOSYS)
+				continue;
+
+			if (errno == EPERM || errno == EACCES) {
 				error("You may not have permission to collect %sstats.\n"
 				      "\t Consider tweaking"
 				      " /proc/sys/kernel/perf_event_paranoid or running as root.",