drm/gud: Don't retry a failed framebuffer flush

drm/gud: Don't retry a failed framebuffer flush

If a framebuffer flush fails the driver will do one retry by requeing the
worker. Currently the worker is used even for synchronous flushing, but a
later patch will inline it, so this needs to change. Thinking about how to
solve this I came to the conclusion that this retry mechanism was a fix
for a problem that was only in the mind of the developer (me) and not
something that solved a real problem.

So let's remove this for now and revisit later should it become necessary.
gud_add_damage() has now only one caller so it can be inlined.

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221122-gud-shadow-plane-v2-2-435037990a83@tronnes.org