drm/i915: Convert intel_dsi to use atomic state

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470755054-32699-11-git-send-email-maarten.lankhorst@linux.intel.com


[mlankhorst: Unbreak bxt_dsi_get_pipe_config]
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>