fbdev/mmp/mmpfb: Do not display boot-up logo

The fbcon module takes care of displaying the logo, if any. Remove
the code form mmpfb. It is probably no tworking as expected, as it
interferes with the framebuffer console. If we want to display the
logo without fbcon, we should implement this in the fbdev core code.

v2:
	* add a note on fbcon interference (Javier)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230907085408.9354-3-tzimmermann@suse.de