drm/todo: Add bootsplash entry

Ease entry for anyone wanting to pick up the bootsplash work by providing
a couple of pointers.

v2: Add Sam as contact (Sam)

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190608152657.36613-6-noralf@tronnes.org