drm/virtio: Handle error from virtio_gpu_resource_id_get

ida_alloc() can return -ENOMEM in the highly unlikely case we run out
of memory.  The current code creates an object with an invalid ID.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20181030165352.13065-1-willy@infradead.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>