perf tests: Add a test case for cumulating callchains

Now it adds a new testcase to verify --children option working
correctly.

Cc: Arun Sharma <asharma@fb.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
5 files changed