drm/i915: Remove WaFbcDisableDpfcClockGating on IVB

Production IVB does not need it. I confirmed this with Art.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -254,12 +254,6 @@ static void ironlake_disable_fbc(struct drm_device *dev)
 		dpfc_ctl &= ~DPFC_CTL_EN;
 		I915_WRITE(ILK_DPFC_CONTROL, dpfc_ctl);
 
-		if (IS_IVYBRIDGE(dev))
-			/* WaFbcDisableDpfcClockGating:ivb */
-			I915_WRITE(ILK_DSPCLK_GATE_D,
-				   I915_READ(ILK_DSPCLK_GATE_D) &
-				   ~ILK_DPFCUNIT_CLOCK_GATE_DISABLE);
-
 		if (IS_HASWELL(dev))
 			/* WaFbcDisableDpfcClockGating:hsw */
 			I915_WRITE(HSW_CLKGATE_DISABLE_PART_1,
@@ -295,10 +289,6 @@ static void gen7_enable_fbc(struct drm_crtc *crtc, unsigned long interval)
 	if (IS_IVYBRIDGE(dev)) {
 		/* WaFbcAsynchFlipDisableFbcQueue:ivb */
 		I915_WRITE(ILK_DISPLAY_CHICKEN1, ILK_FBCQ_DIS);
-		/* WaFbcDisableDpfcClockGating:ivb */
-		I915_WRITE(ILK_DSPCLK_GATE_D,
-			   I915_READ(ILK_DSPCLK_GATE_D) |
-			   ILK_DPFCUNIT_CLOCK_GATE_DISABLE);
 	} else {
 		/* WaFbcAsynchFlipDisableFbcQueue:hsw */
 		I915_WRITE(HSW_PIPE_SLICE_CHICKEN_1(intel_crtc->pipe),