fbdev/sa1100fb: Remove dead code

Motivated because it contains a struct display, which is a fbcon
internal data structure that I want to rename. It seems to have been
formerly used in drivers, but that's very long time ago.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190528090304.9388-6-daniel.vetter@ffwll.ch