improves layouting of kcm in a thin window

allows port and profile selection to wrap into a more rows if the width becomes too small to fit everything. this especially benefits plasma mobile which until now very often had UI elements off screen due to this.

In a wide window it looks almost the same as before, in a thin window items wrap as space runs out.

Wide (old left, new right):

Thin (old left, new right):

I don't love the way it looks, but IMO it's a lot better than going outside the window bounds. There is still a point where it goes off-screen due to other UI elements, but at that point it's at a very small size, see here: