arm64/mpam: resctrl: collect child mon group's monitor data

hulk inclusion
category: feature
feature: ARM MPAM support
bugzilla: 48265
CVE: NA

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For each ctrl group, it's monitoring data should include all it's child
mon groups' monitoring data, these code is borrowed from Intel-RDT for
facilitating users to configure different monitoring strategies.

Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Reviewed-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Reviewed-by: Cheng Jian <cj.chengjian@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>