drm/i915: Group all the global context information together

Create a substruct to hold all the global context state under
drm_i915_private.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170620110547.15947-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_sysfs.c

@@ -209,7 +209,7 @@ i915_l3_write(struct file *filp, struct kobject *kobj,
 	memcpy(*remap_info + (offset/4), buf, count);
 
 	/* NB: We defer the remapping until we switch to the context */
-	list_for_each_entry(ctx, &dev_priv->context_list, link)
+	list_for_each_entry(ctx, &dev_priv->contexts.list, link)
 		ctx->remap_slice |= (1<<slice);
 
 	ret = count;