Revert "Remove product_is_iot."

This reverts commit 14fa562f.

Reason for revert: Broken build on 5772180

error: frameworks/av/media/utils/Android.bp:49:23: unrecognized property "product_variables.product_is_iot"

Bug: 138764596
Change-Id: I37944dfb974e4180a683361f514b404f92b943e5