Disable non-AOSP nnapi extensions on product partition in GSI

The extensions is for OEM. To avoid AOSP code using OEM
extensions mistakenly. GSI denys product to use the extensions
by enabling the following property:

    ro.nnapi.extensions.deny_on_product=true


Bug: 129900377
Test: make gsi_arm64-userdebug, check /system/build.prop
Change-Id: Ia679f1f9c108bd5a164c8cdeb1d73f57da755608
diff --git a/target/board/gsi_system.prop b/target/board/gsi_system.prop
index d768c83..780aadc 100644
--- a/target/board/gsi_system.prop
+++ b/target/board/gsi_system.prop
@@ -4,6 +4,9 @@
 # GSI always disables adb authentication
 ro.adb.secure=0
 
+# GSI disables non-AOSP nnapi extensions on product partition
+ro.nnapi.extensions.deny_on_product=true
+
 # TODO(b/120679683): disable RescueParty before all problem apps solved
 persist.sys.disable_rescue=true