drm/i915/bxt: support for HPD long/short status decoding

All non-GMCH platforms have the same register layout for HPD long/short
status, so let's use this condition instead of HAS_PCH_SPLIT, as the
latter doesn't apply for BXT.

Noticed by Daniel.
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_irq.c

@@ -1428,7 +1428,7 @@ static inline void intel_hpd_irq_handler(struct drm_device *dev,
 		if (port && dev_priv->hpd_irq_port[port]) {
 			bool long_hpd;
 
-			if (HAS_PCH_SPLIT(dev)) {
+			if (!HAS_GMCH_DISPLAY(dev_priv)) {
 				dig_shift = pch_port_to_hotplug_shift(port);
 				long_hpd = (dig_hotplug_reg >> dig_shift) & PORTB_HOTPLUG_LONG_DETECT;
 			} else {