atv: Allow TvSettings to set adb port property

Change-Id: I59d0a9b4cbd3109d3f2f8a310954552fc8071113
diff --git a/atv/private/system_app.te b/atv/private/system_app.te
new file mode 100644
index 0000000..6c7f09b
--- /dev/null
+++ b/atv/private/system_app.te
@@ -0,0 +1,2 @@
+# Allow TvSettings to read/write adb port prop
+set_prop(system_app, adbd_config_prop)