lowpan: Add wpantund to SEPolicy

Bug: b/64399219
Test: Manual
Change-Id: I4f6c7e4e3339ae95e43299bf364edff40d07c796
(cherry picked from commit c8bd93d7e86647ad6880d460f8aa9d24088fad58)
diff --git a/private/system_server.te b/private/system_server.te
index 260d6ce..769b3b7 100644
--- a/private/system_server.te
+++ b/private/system_server.te
@@ -180,6 +180,7 @@
 binder_call(system_server, netd)
 binder_call(system_server, vold)
 binder_call(system_server, wificond)
+binder_call(system_server, wpantund)
 binder_service(system_server)
 
 # Use HALs