fbdev/tdfxfb: Set i2c adapter parent to hardware device

Use the 3dfx hardware device from the Linux device hierarchy as
parent device of the i2c adapter. Aligns the driver with the rest
of the codebase and 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/20230613110953.24176-32-tzimmermann@suse.de