perf report: Add report.cumulate config option

Add report.cumulate config option for setting default value of
callchain accumulation.  It affects the report output only if
perf.data contains callchain info.

A user can write .perfconfig file like below to enable accumulation
by default:

  $ cat ~/.perfconfig
  [report]
  cumulate = true

And it can be disabled through command line:

  $ perf report --no-cumulate

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
1 file changed