fbdev/broadsheetfb: Call device_remove_file() with hardware device

Call device_remove_file() with the same device that has been used
for device_create_file(), which is the hardware device stored in
struct fb_info.device. Prepares fbdev for making struct fb_info.dev
optional.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230613110953.24176-12-tzimmermann@suse.de