drm/i915: Remove zombie async flip vt-d w/a

This async flip vt-d w/a was moved to a different place in
commit 7d396cac ("drm/i195: Make the async flip VT-d workaround
dynamic") but the drm-intel-fixes cherry-pick commit b2d73deb
("drm/i915: Extend the async flip VT-d w/a to skl/bxt") resurrected
the original code as well. So now we have this w/a in two places.
Remove the resurrected zombie code.

Not done as a revert to hopefully prevent any kind of
automagic stable backport.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211208150050.17230-1-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_pm.c

@@ -79,8 +79,6 @@ struct intel_wm_config {
 
 static void gen9_init_clock_gating(struct drm_i915_private *dev_priv)
 {
-	enum pipe pipe;
-
 	if (HAS_LLC(dev_priv)) {
 		/*
 		 * WaCompressedResourceDisplayNewHashMode:skl,kbl
@@ -94,16 +92,6 @@ static void gen9_init_clock_gating(struct drm_i915_private *dev_priv)
 			   SKL_DE_COMPRESSED_HASH_MODE);
 	}
 
-	for_each_pipe(dev_priv, pipe) {
-		/*
-		 * "Plane N strech max must be programmed to 11b (x1)
-		 *  when Async flips are enabled on that plane."
-		 */
-		if (!IS_GEMINILAKE(dev_priv) && intel_vtd_active())
-			intel_uncore_rmw(&dev_priv->uncore, CHICKEN_PIPESL_1(pipe),
-					 SKL_PLANE1_STRETCH_MAX_MASK, SKL_PLANE1_STRETCH_MAX_X1);
-	}
-
 	/* See Bspec note for PSR2_CTL bit 31, Wa#828:skl,bxt,kbl,cfl */
 	intel_uncore_write(&dev_priv->uncore, CHICKEN_PAR1_1,
 		   intel_uncore_read(&dev_priv->uncore, CHICKEN_PAR1_1) | SKL_EDP_PSR_FIX_RDWRAP);