Grant audioserver access to /system/lib64/hw

audioserver uses an always-passthrough Allocator HAL (ashmem / mapper)
whose .so is loaded from /system/lib64/hw.

Test: Modify hal_client_domain macro to not associate client of X HAL
      with hal_x attribute. Play Google Play Movies move -- no denials
      and AV playback works.
Bug: 37160141

Change-Id: I7b88b222aba5361a6c7f0f6bb89705503255a4b1

private/audioserver.te

@@ -13,6 +13,9 @@ binder_call(audioserver, appdomain)
 binder_service(audioserver)
 
 hal_client_domain(audioserver, hal_allocator)
+# /system/lib64/hw for always-passthrough Allocator HAL ashmem / mapper .so
+r_dir_file(audioserver, system_file)
+
 hal_client_domain(audioserver, hal_audio)
 
 userdebug_or_eng(`