fbdev: Acquire framebuffer apertures for firmware devices

When registering a generic framebuffer, automatically acquire ownership
of the framebuffer's I/O range. The device will now be handled by the
aperture helpers. Fbdev-based conflict handling is no longer required.

v2:
	* use fb_ prefix instead of fbm_ (Javier)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220718072322.8927-11-tzimmermann@suse.de