fbdev/au1200fb: Do not display boot-up logo

The fbcon module takes care of displaying the logo, if any. Remove
the code form au1200fb. If we want to display the logo without fbcon,
we should implement this in the fbdev core code.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230907085408.9354-2-tzimmermann@suse.de