drm/i915: Explicitly use ddi buf trans entry 9 for hdmi

BugLink: http://bugs.launchpad.net/bugs/1770565

When the DDI port is in HDMI/DVI mode, it automagically uses the buffer
translations values from entry 9. Let's make that explicit in the code.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1468328376-6380-6-git-send-email-ville.syrjala@linux.intel.com

(cherry picked from commit ed9c77d2)
Signed-off-by: Timo Aaltonen <timo.aaltonen@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

ubuntu/i915/intel_ddi.c

@@ -526,9 +526,9 @@ void intel_prepare_ddi_buffer(struct intel_encoder *encoder)
 		return;
 
 	/* Entry 9 is for HDMI: */
-	I915_WRITE(DDI_BUF_TRANS_LO(port, i),
+	I915_WRITE(DDI_BUF_TRANS_LO(port, 9),
 		   ddi_translations_hdmi[hdmi_level].trans1 | iboost_bit);
-	I915_WRITE(DDI_BUF_TRANS_HI(port, i),
+	I915_WRITE(DDI_BUF_TRANS_HI(port, 9),
 		   ddi_translations_hdmi[hdmi_level].trans2);
 }