drm/i915/dp: fix EHL/JSL max source rates calculation

Only higher voltage sku can support HBR3 so a condition
check added in max source rate calculation for ehl/jsl.

Bspec: 32247, 20598

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210901160402.24816-4-animesh.manna@intel.com

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

@@ -315,7 +315,11 @@ static int icl_max_source_rate(struct intel_dp *intel_dp)
 
 static int ehl_max_source_rate(struct intel_dp *intel_dp)
 {
-	if (intel_dp_is_edp(intel_dp))
+	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
+	struct drm_i915_private *dev_priv = to_i915(dig_port->base.base.dev);
+	enum phy phy = intel_port_to_phy(dev_priv, dig_port->base.port);
+
+	if (intel_dp_is_edp(intel_dp) || is_low_voltage_sku(dev_priv, phy))
 		return 540000;
 
 	return 810000;