arm64/mpam: use snprintf instead of sprintf

hulk inclusion
category: bugfix
bugzilla: 48265
CVE: NA

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snprintf is more safe than sprintf, it is recommended
to use snprintf.

Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>
Reviewed-by: Yang Yingliang <yangyingliang@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>