drm/i915: use DPLL_DVO_HIGH_SPEED for PCH eDP

As with other PCH DP connections.
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_display.c

@@ -3850,7 +3850,7 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 			}
 			dpll |= DPLL_DVO_HIGH_SPEED;
 		}
-		if (is_dp)
+		if (is_dp || intel_encoder_is_pch_edp(&has_edp_encoder->base))
 			dpll |= DPLL_DVO_HIGH_SPEED;
 
 		/* compute bitmask from p1 value */