perf stat: Add support to print counts for fixed times

ufo19890607
2018-01-24T02:43:38Z

From: yuzhoujian <yuzhoujian@didichuxing.com>

Hi Jirka
And how can you control the output for perf stat, if I don't want to use the
"sleep" workload, like some user programs. I want to check the "cycles"
for this program when it just begin to run.

root@node10:/home$ gcc -g -o malloc malloc.c
root@node10:/home$ ./perf stat -e cycles -I 1000 --times-print 3 ./malloc &
[1] 32586
# time counts unit events
1.000094153 2,914,162,979 cycles
2.000323667 3,062,832,799 cycles
3.000443807 3,063,146,609 cycles

Best wishes