Add a TETHER_PRIVILEGED permission and use it where needed.

BUG: 26247383
Change-Id: I73f7227d77926faa9081e83eccb83c8ddee33e08
diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index 1090f90..d81cb29 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -1052,6 +1052,12 @@
     <permission android:name="android.permission.READ_WIFI_CREDENTIAL"
         android:protectionLevel="signature|privileged" />
 
+    <!-- @SystemApi @hide Allows applications to change tether state and run
+         tether carrier provisioning.
+         <p>Not for use by third-party applications. -->
+    <permission android:name="android.permission.TETHER_PRIVILEGED"
+        android:protectionLevel="signature|privileged" />
+
     <!-- @SystemApi @hide Allow system apps to receive broadcast
          when a wifi network credential is changed.
          <p>Not for use by third-party applications. -->