drm/amdgpu: Do not include <linux/fb.h>

Remove unnecessary include statements for <linux/fb.h>. No functional
changes.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20230111130206.29974-5-tzimmermann@suse.de