simpleperf: change the separator of --symbols option from comma to semicolon.

Function name of c++ can have comma, like func2(int, int). So it is not
proper to use comma to separate function names.

Bug: 29826956
Change-Id: I9da4bc178232dad53abdc5735358f3feb608fee4
Test: run simpleperf_unit_test.
4 files changed