vndk-def: Fix sp-hal and vndk-stable computation.

This commit fixes the computation algorithm for sp-hal and vndk-stable.
Before this commit, vndk-stable are determined from a pre-defined set
and sp-hal might include AOSP libraries.  After this commit, we are
adding SP-HAL dependencies to VNDK-stable if the dependency is an AOSP
library.

Test: ./tests/test_elf_linker.py
Change-Id: I7df3374ff49ff33826f496c0fabcb3749efd4fb2