arm64/mpam: only add new domain node to domain list

hulk inclusion
category: bugfix
bugzilla: 48265
CVE: NA

--------------------------------

Only add a new domain to domain list, don't care about exist domain
node.

Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Reviewed-by: Cheng Jian <cj.chengjian@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>