perf_event: define security class and access vectors

This patch allows us to write SELinux policies for the
perf_event_open() syscall LSM hooks added to the kernel in the following
commit:
https://github.com/torvalds/linux/commit/da97e18458fb42d7c00fac5fd1c56a3896ec666e

Bug: 137092007
Change-Id: I0005759eb7a487faebe94a4653e3865343eb441e
diff --git a/private/security_classes b/private/security_classes
index 25b4cba..c0631e9 100644
--- a/private/security_classes
+++ b/private/security_classes
@@ -139,6 +139,8 @@
 
 class xdp_socket
 
+class perf_event
+
 # Property service
 class property_service          # userspace