simpleperf: change default callgraph to use caller mode.
Callgraph in caller mode shows how functions call others, i.e.,
main() -> func1() -> func2(). Instead, callgraph in callee mode shows
how functions are called by others, i.e., func2() <- func1() <- main().
It seems callgraph in caller mode is easier to understand than callee
mode. So change to default option to use caller mode.
Bug: 29574526
Change-Id: I85f104ef7c974bbf7cafd290563e762ba1e0a084
Test: manually check if the default call graph changes.
1 file changed
