aoe: add error handling support for add_disk()

We never checked for errors on add_disk() as this function
returned void. Now that this is fixed, use the shiny new
error handling.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/aoe/aoeblk.c

@@ -417,7 +417,9 @@ aoeblk_gdalloc(void *vp)
 
 	spin_unlock_irqrestore(&d->lock, flags);
 
-	device_add_disk(NULL, gd, aoe_attr_groups);
+	err = device_add_disk(NULL, gd, aoe_attr_groups);
+	if (err)
+		goto out_disk_cleanup;
 	aoedisk_add_debugfs(d);
 
 	spin_lock_irqsave(&d->lock, flags);
@@ -426,6 +428,8 @@ aoeblk_gdalloc(void *vp)
 	spin_unlock_irqrestore(&d->lock, flags);
 	return;
 
+out_disk_cleanup:
+	blk_cleanup_disk(gd);
 err_tagset:
 	blk_mq_free_tag_set(set);
 err_mempool: