Add 3.5x3.5mm QFN-20 with 2mm pad.
Created by: ObKo
Also known as TI's S-PVQFN-N20
http://www.ti.com/lit/ml/mpqf239/mpqf239.pdf
Generated by kicad-footprint-generator.
Associated with: https://github.com/pointhi/kicad-footprint-generator/pull/339, https://github.com/KiCad/kicad-symbols/pull/1728