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

Bug: 35097918
Test: manual
Change-Id: I84a1eaae99ebd04f0f8a6990b2f85ed7f2e11182
(cherry picked from commit 6e3a5d005366cc3f785bd8fee7c2eb6d4173d939)
diff --git a/public/hal_bluetooth.te b/public/hal_bluetooth.te
index a3497a7..3e132b9 100644
--- a/public/hal_bluetooth.te
+++ b/public/hal_bluetooth.te
@@ -20,3 +20,6 @@
 
 # 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;