drm/vkms: convert to use faux_device

drm/vkms: convert to use faux_device

The vkms driver does not need to create a platform device, as there is
no real platform resources associated it,  it only did so because it was
simple to do that in order to get a device to use for resource
management of drm resources.  Change the driver to use the faux device
instead as this is NOT a real platform device.

Tested-by: Louis Chauvet <louis.chauvet@bootlin.com>
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Haneen Mohammed <hamohammed.sa@gmail.com>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Melissa Wen <melissa.srw@gmail.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: David Airlie <airlied@gmail.com>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/2025070147-antics-pleat-edd2@gregkh