perf tests: Compensate lower sample freq with longer test loop

Doesn't work for me:

./perf test -v 19
19: Test software clock events have valid period values    :
--- start ---
mmap size 528384B
mmap size 528384B
All (0) samples have period value of 1!
---- end ----
Test software clock events have valid period values: FAILED!

Compensate the lower freq introduced in 67c1e4a5 with a longer loop,
Signed-off-by: NAdrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/5281D3B8.2030104@intel.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/sw-clock.c

@@ -9,7 +9,7 @@
 #include "util/cpumap.h"
 #include "util/thread_map.h"
 
-#define NR_LOOPS  1000000
+#define NR_LOOPS  10000000
 
 /*
  * This test will open software clock events (cpu-clock, task-clock)