simpleperf: Use PMU's cpumask if available

Some PMU events only support profiling from dedicated cpus.  For those
events there are cpumask files in the /sys/bus/event_source/devices/<PMU>
directory.  So override the cpu setting for them.

Test: manually tested with a PMU has the cpumask file
Change-Id: I5e50a7d6f88cb0bc80b45e774cf048116698b3de
Signed-off-by: Namhyung Kim <namhyung@google.com>
4 files changed