Bluetooth: Enable /proc access for vendor library low power control

Bug: 35097918
Test: manual
Change-Id: I84a1eaae99ebd04f0f8a6990b2f85ed7f2e11182

public/hal_bluetooth.te

@@ -20,3 +20,6 @@ allow hal_bluetooth self:capability2 wake_alarm;
 
 # Allow write access to bluetooth-specific properties
 set_prop(hal_bluetooth, bluetooth_prop)
+
+# /proc access (bluesleep etc.).
+allow hal_bluetooth proc_bluetooth_writable:file rw_file_perms;