drm/i915: set stc evict disable lra evict w/a

Our workaround list kindly lists that this new default value needs to
be updated in Bspec. Naturally, this did not happen.

Acked-by: Ben Widawsky <ben@bwidawsk.net>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 1a6bb61..7506a72 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8878,6 +8878,10 @@
 	I915_WRITE(WM2_LP_ILK, 0);
 	I915_WRITE(WM1_LP_ILK, 0);
 
+	/* clear masked bit */
+	I915_WRITE(CACHE_MODE_0,
+		   CM0_STC_EVICT_DISABLE_LRA_SNB << CM0_MASK_SHIFT);
+
 	I915_WRITE(GEN6_UCGCTL1,
 		   I915_READ(GEN6_UCGCTL1) |
 		   GEN6_BLBUNIT_CLOCK_GATE_DISABLE |