i915: Don't attempt to short-circuit object_wait_rendering by checking domains.

This could return early when reading after writing a buffer, if somebody
had already put it on the flushing list (write domains are 0, but still
active), leading to glReadPixels failure.
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Dave Airlie <airlied@linux.ie>

drivers/gpu/drm/i915/i915_gem.c

@@ -1455,11 +1455,9 @@ i915_gem_object_set_domain_range(struct drm_gem_object *obj,
 						  read_domains, write_domain);
 
 	/* Wait on any GPU rendering to the object to be flushed. */
-	if (obj->write_domain & ~(I915_GEM_DOMAIN_CPU | I915_GEM_DOMAIN_GTT)) {
 	ret = i915_gem_object_wait_rendering(obj);
 	if (ret)
 		return ret;
-	}
 
 	if (obj_priv->page_cpu_valid == NULL) {
 		obj_priv->page_cpu_valid = drm_calloc(1, obj->size / PAGE_SIZE,