XF86_PDEV_SERVER_FD is defined since:
commit 5fb641a29b
Author: Hans de Goede <hdegoede@redhat.com>
Date: Mon Jan 13 12:03:46 2014 +0100
hotplug: Extend OdevAttributes for server-managed fd support
ifdef'ing for it is a leftover from the external xf86-video-modesetting.
Signed-off-by: Daniel Martin <consume.noise@gmail.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>