Simpleperf: add test about cpu hot-plug.

On device like N7(flo), because of a kernel bug, if a cpu is hotplugged
while there are hardware events monitored not on that cpu, the kernel
arrives in an error state that no further hardware events can be monitored.
This test is used to detect the kernel bug.

Bug: 19863147
Change-Id: Ieed4fef174373b5fe62afacf8197e839685893df
2 files changed