Create LLNDK vendor variants when DeviceVndkVersion is not set

The LLNDK vendor variants need to exist even when the VNDK is not
being used in order for the next patch to list them once the global
maps are removed.

Bug: 176904285
Test: m checkbuild
Change-Id: Ib29ede455d5b6a4b7d3f4685db8fba6d32025314