drm/i915/ehl: Support HBR3 on EHL combo PHY

Unlike ICL, EHL's combo PHYs can support HBR3 data rates.  Note that
this just extends the upper limit; we will continue to honor the max
data rate specified in the VBT in cases where it is lower than HBR3.
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190605211832.23945-1-matthew.d.roper@intel.comReviewed-by: Manasi Navare <manasi.d.navare@intel.com>

drivers/gpu/drm/i915/intel_dp.c

@@ -332,6 +332,7 @@ static int icl_max_source_rate(struct intel_dp *intel_dp)
 	enum port port = dig_port->base.port;
 
 	if (intel_port_is_combophy(dev_priv, port) &&
+	    !IS_ELKHARTLAKE(dev_priv) &&
 	    !intel_dp_is_edp(intel_dp))
 		return 540000;