wpa_supplicant: Make objects depend on the .config file

wpa_supplicant: Make objects depend on the .config file

The source code compiles into different objects depending on
the contents of .config. Therefore, the objects should depend
on .config.

Previously, only the executables depended on .config. This meant
that they were re-linked when .config changed. But that relink
process used the old (and now wrong) objects.