arm64/mpam: Add helper for getting MSCs' configuration

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

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resctrl sysfs need to show MSCs' configuration applied, we can get this
intermediate data from mpam config structure live in each component
straightforwardly, but for safety we look at the exact value of those
registers in any cases, althought it will spend a few time.

We add independent helper separated from do_device_sync() according to
James' implementation, purposely reading single device for one component,
it is because all devices in one component will be uniformly configured
in one configuration process, so reading single device is sufficient for
getting each component's configuration.

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>