drm/pl111: Run DRM default client setup

Call drm_client_setup_with_color_mode() to run the kernel's default
client setup for DRM. Set fbdev_probe in struct drm_driver, so that
the client setup can start the common fbdev client.

v5:
- select DRM_CLIENT_SELECTION

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240924071734.98201-33-tzimmermann@suse.de