According to screen driver this device screen is actually 16 bit RGB565 (https://github.com/DrUm78/linux/blob/FunKey_S/drivers/staging/fbtft/fb_st7789v.c#L137).
This also fixes the color banding issues we had before and boomshine doesn't segfault anymore. Also building rockpaint now that's possible.
Change-Id: Icee49c347fbfabc79e0040314ec148cb77ca6325