perf time-utils: Prevent percentage time range overlap

Prevent percentage time range overlap. This is only a 1 nanosecond
change but makes the results more logical e.g. a sample cannot be in
both the first 10% and the second 20%.

Note, there is a later patch that adds a test for time-utils.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20190604130017.31207-15-adrian.hunter@intel.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>