drm/i915: initialize DDI buffer translations

DDI is introduced starting with Haswell GPU generation. So to simplify its
management in the future, we also add intel_ddi.c to hold all the
DDI-related items.

Buffer translations for DDI links must be initialized prior to enablement.
For FDI and DP, first 9 pairs of values are used to select the connection
parameters. HDMI uses the last pair of values and ignores the first 9
pairs. So we program HDMI values in both cases, which allows HDMI to work
over both FDI and DP-friendly buffers.

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 101c4d4..096a1b1 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6806,6 +6806,8 @@
 
 	intel_init_pm(dev);
 
+	intel_prepare_ddi(dev);
+
 	intel_init_display(dev);
 
 	if (IS_GEN2(dev)) {