Sepolicy: Give asan_extract access to powerctl

rc-style powerctl has beem removed. Accordingly, asan_extract now
needs access to sys.powerctl directly.

(orginally commit: 82672089)

Bug: 36458146
Bug: 38241921
Test: Builds and boots.
Change-Id: I7d6e583f5e98b671986a2071abf157c86e288a10