drm/i915: drop WaSetupGtModeTdRowDispatch:snb

This reverts the regressing

commit 6547fbdbfff62c99e4f7b4f985ff8b3454f33b0f
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Fri Dec 14 23:38:29 2012 +0100

    drm/i915: Implement WaSetupGtModeTdRowDispatch

that causes GPU hangs immediately on boot.

Reported-by: Leo Wolf <jclw@ymail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=79996
Cc: stable@vger.kernel.org (v3.8+)
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
[Jani: amended the commit message slightly.]
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_pm.c

@@ -5469,11 +5469,6 @@ static void gen6_init_clock_gating(struct drm_device *dev)
 	I915_WRITE(_3D_CHICKEN,
 		   _MASKED_BIT_ENABLE(_3D_CHICKEN_HIZ_PLANE_DISABLE_MSAA_4X_SNB));
 
-	/* WaSetupGtModeTdRowDispatch:snb */
-	if (IS_SNB_GT1(dev))
-		I915_WRITE(GEN6_GT_MODE,
-			   _MASKED_BIT_ENABLE(GEN6_TD_FOUR_ROW_DISPATCH_DISABLE));
-
 	/* WaDisable_RenderCache_OperationalFlush:snb */
 	I915_WRITE(CACHE_MODE_0, _MASKED_BIT_DISABLE(RC_OP_FLUSH_ENABLE));