drm/tiny/panel-mipi-dbi: Use fbdev-dma

Implement fbdev emulation with fbdev-dma. Fbdev-dma now supports
damage handling, which is required by panel-mipi-dbi. Avoids the
overhead of fbdev-generic's additional shadow buffering. No functional
changes.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: "Noralf Trønnes" <noralf@tronnes.org>
Acked-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240419083331.7761-39-tzimmermann@suse.de