perf report: Remove the time slices number limitation

perf report: Remove the time slices number limitation

Previously it was only allowed to use at most 10 time slices in 'perf
report --time'.

This patch removes this limitation.
For example, following command line is OK (12 time slices)

perf report --stdio --time 1%/1,1%/2,1%/3,1%/4,1%/5,1%/6,1%/7,1%/8,1%/9,1%/10,1%/11,1%/12

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Suggested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Reviewed-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1515596433-24653-8-git-send-email-yao.jin@linux.intel.com
[ No need to check for NULL to call free, use zfree ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>