drm/i915: Assume we implement WaStripsFansDisableFastClipPerformanceFix:snb

Based on the name, the workaround we implement is
WaStripsFansDisableFastClipPerformanceFix. Unfortunately there's no
description in the w/a database, so this is just a guess.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NAntti Koskipää <antti.koskipaa@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -4695,6 +4695,7 @@ static void gen6_init_clock_gating(struct drm_device *dev)
 		   GEN6_RCPBUNIT_CLOCK_GATE_DISABLE |
 		   GEN6_RCCUNIT_CLOCK_GATE_DISABLE);
 
+	/* WaStripsFansDisableFastClipPerformanceFix:snb */
 	/* Bspec says we need to always set all mask bits. */
 	I915_WRITE(_3D_CHICKEN3, (0xFFFF << 16) |
 		   _3D_CHICKEN3_SF_DISABLE_FASTCLIP_CULL);