ANDROID: GKI: perf: Add field for struct perf_event

Adds the new struct variable "readable_on_cpus" to reduce the ABI
diff. The Full feature is under commit f994cb43 ("perf/core:
Add support for PMUs that can be read from more than 1 CPU").

Bug: 148872640
Test: compile test
(cherry picked from commit f994cb43)
[Only cherry-picked the ABI difference]
Signed-off-by: Will McVicker <willmcvicker@google.com>
Change-Id: If46a71163efde2245e955b23da58550e21082e62