drm/i915: make DP training try a little harder

When trying to do channel equalization, we need to make sure we still
have clock recovery on all lanes while training.  We also need to try
clock recovery again if we lose the clock or if channel eq fails 5
times.  We'll try clock recovery up to 5 more times before giving up
entirely.

Gets suspend/resume working on my Vaio again and brings us back into
compliance with the DP training sequence spec.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>