[PATCH i-g-t] tests: Add a test for device hot unplug

[Chris Wilson]

Quoting Janusz Krzysztofik (2020-04-07 11:13:53)
> +struct hotunplug {
> +       int chipset;
> +       struct {
> +               int drm;
> +               int sysfs_dev;
> +               int sysfs_bus;
> +       } fd;
> +};
> +
> +/* Helpers */
> +
> +static void prepare(struct hotunplug *priv)
> +{
> +       /* open the driver */
> +       priv->fd.drm = __drm_open_driver(priv->chipset);

Hmm. How do we avoid chipset and use a specific device? For the
inevitable extension to multi-device validation.

I guess we will need an open_by_pciid(). Since we are simulating
hotplugs, we should be fortunate enough that the pci topology doesn't
actually change!
-Chris