xen-netback: remove unecessary condition check before debugfs_remove_recursive

debugfs_remove_recursive has taken IS_ERR_OR_NULL into account. So just
remove the condition check before debugfs_remove_recursive.
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/xen-netback/netback.c

@@ -1660,7 +1660,6 @@ module_init(netback_init);
 static void __exit netback_fini(void)
 {
 #ifdef CONFIG_DEBUG_FS
-	if (!IS_ERR_OR_NULL(xen_netback_dbg_root))
 	debugfs_remove_recursive(xen_netback_dbg_root);
 #endif /* CONFIG_DEBUG_FS */
 	xenvif_xenbus_fini();