zenfone9: Convert factory mnt_point symlink to install_symlink targets

Change-Id: I4882509a60545416223f25ccab12142e05e127a6
diff --git a/Android.bp b/Android.bp
index 27c8df7..013e76b 100644
--- a/Android.bp
+++ b/Android.bp
@@ -15,3 +15,10 @@
         "vendor.nxp.eventprocessor@1.0::INxpEseEvtProcessor",
     ],
 }
+
+install_symlink {
+    name: "mnt_point_factory_symlink",
+    vendor: true,
+    installed_location: "factory",
+    symlink_target: "/mnt/vendor/persist",
+}