simpleperf: prepare for selinux change.

To work with controlling perf_events via selinux:

1. Check security.perf_harden property at the entry of simpleperf.
2. Record tracepoint raw data only when running as root.

Bug: 139860059
Test: run simpleperf_unit_test.
Change-Id: I40082de0010949e54fb707f385220157a71f266b
2 files changed