drm/i915: add another virtual PCH bridge for passthrough support

Some configs use the P2X type but some use a P3X type PCH, so add that
to the detect_pch function so things work correctly.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Allen Kay <allen.m.kay@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1458160290-16710-1-git-send-email-jbarnes@virtuousgeek.org

drivers/gpu/drm/i915/i915_drv.c

@@ -504,6 +504,7 @@ void intel_detect_pch(struct drm_device *dev)
 				WARN_ON(!IS_SKYLAKE(dev) &&
 					!IS_KABYLAKE(dev));
 			} else if ((id == INTEL_PCH_P2X_DEVICE_ID_TYPE) ||
+				   (id == INTEL_PCH_P3X_DEVICE_ID_TYPE) ||
 				   ((id == INTEL_PCH_QEMU_DEVICE_ID_TYPE) &&
 				    pch->subsystem_vendor == 0x1af4 &&
 				    pch->subsystem_device == 0x1100)) {

drivers/gpu/drm/i915/i915_drv.h

@@ -2665,6 +2665,7 @@ struct drm_i915_cmd_table {
 #define INTEL_PCH_SPT_DEVICE_ID_TYPE		0xA100
 #define INTEL_PCH_SPT_LP_DEVICE_ID_TYPE		0x9D00
 #define INTEL_PCH_P2X_DEVICE_ID_TYPE		0x7100
+#define INTEL_PCH_P3X_DEVICE_ID_TYPE		0x7000
 #define INTEL_PCH_QEMU_DEVICE_ID_TYPE		0x2900 /* qemu q35 has 2918 */
 
 #define INTEL_PCH_TYPE(dev) (__I915__(dev)->pch_type)