perf stat record: Do not allow record with multiple runs mode

perf stat record: Do not allow record with multiple runs mode

We currently don't support storing multiple session in perf.data,
so we can't allow -r option in stat record.

  $ perf stat -e cycles -r 2 record ls
  Cannot use -r option with perf stat record.

Committer note:

Before this patch we would a perf.data file such as:

  $ perf stat -e cycles -r 2 record ls
  <SNIP>

   Performance counter stats for 'ls' (2 runs):

         3,935,236      cycles

       0.002353261 seconds time elapsed                                          ( +-  4.76% )

  $ perf report -D | grep PERF_RECORD | grep ROUND
  0xf0 [0]: failed to process type: 16
  Error:
  failed to process sample
  $

Reported-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1446734469-11352-10-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>