Mode set sequence requires that we start training, then enable the
panel, then complete training.  So split the DP training function into
two parts; the first enables the DP port and sets training pattern 1 and
the second completes the training.

As part of this, remove some redundant function args from the various DP
handling functions and use the intel_dp fields everywhere we can.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
[ickle: removed first ironlake_edp_backlight_on() on advice of jbarnes]
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>