drm/i915: Don't update display FIFO watermark on IGDNG

Signed-off-by: NZhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: NEric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/i915_drv.h

@@ -892,7 +892,7 @@ extern int i915_wait_ring(struct drm_device * dev, int n, const char *caller);
 #define SUPPORTS_INTEGRATED_DP(dev)	(IS_G4X(dev) || IS_IGDNG(dev))
 #define I915_HAS_HOTPLUG(dev) (IS_I945G(dev) || IS_I945GM(dev) || IS_I965G(dev))
 /* dsparb controlled by hw only */
-#define DSPARB_HWCONTROL(dev) (IS_G4X(dev))
+#define DSPARB_HWCONTROL(dev) (IS_G4X(dev) || IS_IGDNG(dev))
 
 #define PRIMARY_RINGBUFFER_SIZE         (128*1024)