In TW, we mostly use fbdev vesafb and efifb drivers for early-boot display
output and as fallback.

This has a number of problems, such as

  * Most modern Wayland compositors don't support fbdev any longer. Even X'
support is bolted-on. Generally, userspace support for fbdev is slowly fading.
See bug 1187154.

  * Handover from fbdev to native DRM drivers is unreliable and can result in
stuck systems during boot. See bug 1181913.

Therefore, replace TW's fbdev drivers with simpledrm and maybe other DRM
drivers.