PCI: hotplug: pciehp: Removed check for hotplug of display devices

Removed check to prevent hotplug of display devices within pciehp.
Originally this was thought to have been required within the PCI
Hotplug specification for some legacy devices.  However there is
no such requirement in the most recent revision. The check prevents
hotplug of not only display devices but also computational GPUs
which require serviceability.

Signed-off-by: Praveen Kalamegham <praveen@nextio.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>