Draft: firmware-samsung-kminilte: move wpa_supp. changes to new subpackage

This ensures that wpa_supplicant is actually installed (and it's .conf is available) when the post-install script runs. It fixes a problem where the post-install script might run before this conf file is installed, causing it to fail.

@scjorge: I did a quick build test and it seems fine (the install doesn't fail), but it would be useful if you could try it too :)