fbdev/efifb: Do not use struct fb_info.apertures

Acquire ownership of the firmware scanout buffer by calling Linux'
aperture helpers. Remove the use of struct fb_info.apertures and do
not set FBINFO_MISC_FIRMWARE; both of which previously configured
buffer ownership.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221219160516.23436-12-tzimmermann@suse.de