drm/i915: Convert resume to atomic.

Instead of all the ad-hoc updating, duplicate the old state first
before reading out the hw state, then restore it.

intel_display_resume is a new function that duplicates the sw state,
then reads out the hw state, and commits the old state.

intel_display_setup_hw_state now only reads out the atomic state.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90396


Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>