drm/i915: Add a pipeless ivybridge configuration

FIXME: This is based on some HW being used for a demo. We should
probably wait until we have confirmation on the IDs before upstreaming
this patch.

v2: Use GEN7_FEATURES (Chris)

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>