drm/i915/kbl: Add WaDisableFenceDestinationToSLM for A0

Add this workaround for kbl revid A0 only.

v2: rebase
v3: carve out a non related workaround (Chris)

References: HSD#1911714
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465309159-30531-9-git-send-email-mika.kuoppala@intel.com

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -1199,6 +1199,11 @@ static int kbl_init_workarounds(struct intel_engine_cs *engine)
 	I915_WRITE(GEN8_GARBCNTL, (I915_READ(GEN8_GARBCNTL) |
 				   GEN9_GAPS_TSV_CREDIT_DISABLE));
 
+	/* WaDisableFenceDestinationToSLM:kbl (pre-prod) */
+	if (IS_KBL_REVID(dev_priv, KBL_REVID_A0, KBL_REVID_A0))
+		WA_SET_BIT_MASKED(HDC_CHICKEN0,
+				  HDC_FENCE_DEST_SLM_DISABLE);
+
 	return 0;
 }