This should allow BIOS fb inheritance to work on ILK+ machines too.

v2: handle tiled BIOS fbs (Kristian)
    split out common bits (Jesse)
v3: alloc fb obj out in _init
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>