Revert "drm/i915: set dummy page for stolen objects"

Since for_each_sg_page supports already memory w/o backing pages we can
revert the corresponding workaround.

This reverts commit 5bd4687.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem_stolen.c

@@ -222,8 +222,8 @@ i915_pages_create_for_stolen(struct drm_device *dev,
 	}
 
 	sg = st->sgl;
-	/* we set the dummy page here only to make for_each_sg_page work */
-	sg_set_page(sg, dev_priv->gtt.scratch_page, size, offset);
+	sg->offset = offset;
+	sg->length = size;
 
 	sg_dma_address(sg) = (dma_addr_t)dev_priv->mm.stolen_base + offset;
 	sg_dma_len(sg) = size;