drm/mcde: Do not use dirty GEM FB handling

This driver has no way to handle damage, the reason the
drm_gem_fb_create_with_dirty() was used was because I had the
ambition that the driver would only send out updates to DSI
command displays whenever something changed, so as to
minimize traffic.

It turns out this ambition with command mode isn't working
in practice because all the MCDE does is to create a
continuous stream of DSI commands and while it is possible to
send single frame updates with it, it's not been worthwhile.
So we are just setting up continuous updates.

Reported-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/dri-devel/0e789778-03ca-e3cb-9c94-e8b55573894c@suse.de/


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230313155138.20584-24-tzimmermann@suse.de