drm/i915: move dri1 vblank stubs to i915_dma.c

i915_dma.c contains most of the old dri1 horror-show, so move
the remaining bits there, too. The code has been removed and
the only thing left are some stubs to ensure that userspace
doesn't try to use this stuff. vblank_pipe_set only returns 0
without any side-effects, so we can even stub it out with
the canonical drm_noop.

v2: Rebase against ENODEV changes.

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