Revert "drm/i915: Try harder to complete DP training pattern 1"

This reverts commit 24773670.

If (for whatever reason) the DP sink device never asks for the maximal
voltage level, we never don't hit the check that should bail us out
after 5 retries of the same voltage. Which leads to an endless loop in
the DP link training code, which hangs the driver.

Now some more DP link training experiments on eDP panels seem to
indicate that our training algorithm isn't robust enough anyway and
needs more work. Hence for 3.7-fixes, let's just revert the regressing
commit instead of trying to apply more duct-tape.

Reported-by: Oleksij Rempel <bug-track@fisher-privat.net>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>