drm/radeon: Use video aperture helpers

DRM's aperture functions have long been implemented as helpers
under drivers/video/ for use with fbdev. Avoid the DRM wrappers by
calling the video functions directly.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: Xinhui Pan <Xinhui.Pan@amd.com>
Acked-by: Javier Martinez Canillas <javierm@redhat.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240930130921.689876-16-tzimmermann@suse.de