Draft: Add S40framebuffer-module-linux to probe simpledrm or simplefb

Currently some Debian kernels are built with the simplefb driver built in for simple-framebuffer devices. The more modern alternative to it is simpledrm. It is possible we might switch to that, and we might even enable it as a module to avoid having the drm dependency as built-in.

Furthermore, if we build kernels with SYSFB_SIMPLEFB=y, the platform drivers like efifb and vesafb can work through either simpledrm or simplefb depending on which is available. Unfortunately, they sometimes do not get probed automatically, specifically in the most prominent efifb case.

Try to probe simpledrm in an init script on Linux systems with a fallback to simplefb, so the platform drivers can still work in the above configuration.

Also see: kernel-team/linux!1312 (closed)

(Not tested in installer yet, will do later.)