gpu: drm: virtio: code cleanup

The fault handler code is commented since v4.2.
If there is no plan to enable the fault handler
code in future, we can remove this dead code.

Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20180703153353.GA3375@jordon-HP-15-Notebook-PC


Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>