drm/sysfb: Add custom plane state
The plane-state type struct drm_sysfb_plane_state will store the
helper for blitting to the scanout buffer.
v2:
- add variable for duplicated shadow-plane state (Javier)
- fix build error
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20250918154207.84714-2-tzimmermann@suse.de