This reverts commit cfecde43.

The commit was first created as an attempt to fix LVDS initialiazation
on Ironlake. Testing revealed that it didn't fix that, but it was
assumed to still be correct anyway.

Subsequent testing has revealed that this commit has caused other
regressions:

  * Change in VBlank interrupt frequency causing 60% 3D performance regression
    http://bugs.freedesktop.org/show_bug.cgi?id=27698

  * Black screen on G45
    http://bugs.freedesktop.org/show_bug.cgi?id=27733

So revert this buggy code for now to revisit later when we can fix
actual bugs without causing these regressions.
Signed-off-by: NCarl Worth <cworth@cworth.org>
Signed-off-by: NEric Anholt <eric@anholt.net>