drm/i915: Fix cpt/ppt max pre-emphasis

cpt/ppt support pre-emphasis level 3. Let's actually declare
support for it, instead of clamping things to level 2.

Also tweak the if-ladder in intel_dp_voltage_max() to match
intel_dp_pre_emphasis_max() to make it easier to compare them.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200512174145.3186-2-ville.syrjala@linux.intel.comReviewed-by: José Roberto de Souza <jose.souza@intel.com>

drivers/gpu/drm/i915/display/intel_dp.c

@@ -4000,12 +4000,11 @@ intel_dp_voltage_max(struct intel_dp *intel_dp)
 
 	if (HAS_DDI(dev_priv))
 		return intel_ddi_dp_voltage_max(encoder);
-	else if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
+	else if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv) ||
+		 (HAS_PCH_CPT(dev_priv) && port != PORT_A))
 		return DP_TRAIN_VOLTAGE_SWING_LEVEL_3;
 	else if (IS_IVYBRIDGE(dev_priv) && port == PORT_A)
 		return DP_TRAIN_VOLTAGE_SWING_LEVEL_2;
-	else if (HAS_PCH_CPT(dev_priv) && port != PORT_A)
-		return DP_TRAIN_VOLTAGE_SWING_LEVEL_3;
 	else
 		return DP_TRAIN_VOLTAGE_SWING_LEVEL_2;
 }
@@ -4019,7 +4018,8 @@ intel_dp_pre_emphasis_max(struct intel_dp *intel_dp, u8 voltage_swing)
 
 	if (HAS_DDI(dev_priv)) {
 		return intel_ddi_dp_pre_emphasis_max(encoder, voltage_swing);
-	} else if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv)) {
+	} else if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv) ||
+		   (HAS_PCH_CPT(dev_priv) && port != PORT_A)) {
 		switch (voltage_swing & DP_TRAIN_VOLTAGE_SWING_MASK) {
 		case DP_TRAIN_VOLTAGE_SWING_LEVEL_0:
 			return DP_TRAIN_PRE_EMPH_LEVEL_3;