The driver sets struct fb_info.bl_dev to the correct backlight
device. Thus rely on the backlight core code to match backlight
and framebuffer devices, and remove the extra check_fb() function
from struct backlight_ops.

v3:
	* use 'check_fb()' in commit message (Andy)
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Robin van der Gracht <robin@protonic.nl>
Acked-by: Robin van der Gracht <robin@protonic.nl>
Acked-by: Andy Shevchenko <andy@kernel.org>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20240305162425.23845-3-tzimmermann@suse.deSigned-off-by: Lee Jones <lee@kernel.org>