initial displaylink kms driver + drm hotplug

[Dave Airlie]

This series contains some changes to the drm to allow for better hotplug
support for usb devices, along with the initial displaylink KMS driver.

This relies on an fbdev patch that is in fbdev-next from Kay Sievers.
(remove sysfs framebuffer device with USB .disconnect)

The initial changes just allow us to disconnect userspace/sysfs stuff properly
then on close of the device we clean up things properly.

This and some other patches it relies on are in my pfdo git tree udl-unplug branch.

Dave.