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
Merged-In: Ia679f1f9c108bd5a164c8cdeb1d73f57da755608
(cherry picked from commit 3c6fde2d)