drm/client: Hack: Add bootsplash example

An example to showcase the client API.

TODO:
- A bootsplash client needs a way to tell drm_fb_helper to stay away,
  otherwise it will chime in on setup and hotplug.
  Most DRM drivers register fbdev before calling drm_dev_register() (the
  generic emulation is an exception). This have to be reversed for
  bootsplash to fend off fbdev.
- Probably need some way to determine which is the primary display/device
  on multi DRM device systems.
- Maybe do handover from early/simple DRM driver

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Patch-mainline: dri-devel Archive on lore.kernel.org @ 23/05/19, 15:44:13
Link: https://patchwork.kernel.org/project/dri-devel/patch/20190523134413.4210-9-noralf@tronnes.org/


[stalek@codeaurora.org: write a paragraph that describes the config symbol fully].

Change-Id: Iba4f0d19dc40885e5cd4dcaac02e3e5ebed8b8a9
Signed-off-by: Narender Ankam <nankam@codeaurora.org>
Signed-off-by: Shubham Talekar <stalek@codeaurora.org>