drm/mediatek: Remove error check from fbdev setup

Remove the error check from the fbdev setup function. The function
will print a warning.

v2:
	* fix subject line

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200408082641.590-6-tzimmermann@suse.de