drm/i915/cnl: Add missing type case.

Paulo had noticed that inside cnl_ddi_vswing_program
the case was handling voltage but with no indication
of type where a missing type could also take us to that
path. So my first attempt was to add a message to
let clear who trigger that path.

However DK had a better idea that is to handle the
missed type sooner before it might take to that path.
So this v2 here uses his approach.

v2: Handle missed type sooner.

Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170710205852.28352-1-rodrigo.vivi@intel.com

drivers/gpu/drm/i915/intel_ddi.c

@@ -1979,9 +1979,12 @@ static void cnl_ddi_vswing_sequence(struct intel_encoder *encoder, u32 level)
 	if ((intel_dp) && (type == INTEL_OUTPUT_EDP || type == INTEL_OUTPUT_DP)) {
 		width = intel_dp->lane_count;
 		rate = intel_dp->link_rate;
-	} else {
+	} else if (type == INTEL_OUTPUT_HDMI) {
 		width = 4;
 		/* Rate is always < than 6GHz for HDMI */
+	} else {
+		MISSING_CASE(type);
+		return;
 	}
 
 	/*