Memory layout transition:

* the 2D driver initializes MC_FB_LOCATION and related registers sanely
* the DRM deduces the layout from these registers
* clients use the new SETPARAM ioctl to tell the DRM where they think the
framebuffer is located in the card's address space
* the DRM uses all this information to check client state and fix it up if
necessary

This is a prerequisite for things like direct rendering with IGP chips and
video capturing.