drm/i915/bdw: Remove BDW preproduction W/As until C stepping.

Let's clean this a bit

v2: Rebase after other Mika's patch that removed some BDW production workarounds.
v3: Removed stepping info.
Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -5654,16 +5654,6 @@ static void broadwell_init_clock_gating(struct drm_device *dev)
 	I915_WRITE(WM2_LP_ILK, 0);
 	I915_WRITE(WM1_LP_ILK, 0);
 
-	/* FIXME(BDW): Check all the w/a, some might only apply to
-	 * pre-production hw. */
-
-
-	I915_WRITE(GAMTARBMODE, _MASKED_BIT_ENABLE(ARB_MODE_BWGTLB_DISABLE));
-
-	I915_WRITE(_3D_CHICKEN3,
-		   _MASKED_BIT_ENABLE(_3D_CHICKEN_SDE_LIMIT_FIFO_POLY_DEPTH(2)));
-
-
 	/* WaSwitchSolVfFArbitrationPriority:bdw */
 	I915_WRITE(GAM_ECOCHK, I915_READ(GAM_ECOCHK) | HSW_ECOCHK_ARB_PRIO_SOL);
 

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -712,13 +712,12 @@ static int bdw_init_workarounds(struct intel_engine_cs *ring)
 		return ret;
 
 	/* WaDisablePartialInstShootdown:bdw */
-	/* WaDisableThreadStallDopClockGating:bdw */
-	/* FIXME: Unclear whether we really need this on production bdw. */
+	/* WaDisableThreadStallDopClockGating:bdw (pre-production) */
 	intel_ring_emit_wa(ring, GEN8_ROW_CHICKEN,
 			   _MASKED_BIT_ENABLE(PARTIAL_INSTRUCTION_SHOOTDOWN_DISABLE
 					     | STALL_DOP_GATING_DISABLE));
 
-	/* WaDisableDopClockGating:bdw May not be needed for production */
+	/* WaDisableDopClockGating:bdw */
 	intel_ring_emit_wa(ring, GEN7_ROW_CHICKEN2,
 			   _MASKED_BIT_ENABLE(DOP_CLOCK_GATING_DISABLE));