drm/i915: pageflip fixes

This patch brings the tree up to date with some fixes that were in a
more recent version of the page flipping patch you applied.  It fixes
pre-965 flip support, removes a leftover hack that forced alignment,
and initializes the pipe & plane CRTC mappings.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eric Anholt <eric@anholt.net>