drm/i915: move dri1 dungeon out of dev_priv

Also, move dev_priv->counter there, it's only used in i915_dma.c

And also move the dri1 dungeon at the end of dev_priv where no one
cares about it.

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>