arm64/mpam: refactor device tree structure to support multiple devices

ascend inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4L735


CVE: NA

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The process of MPAM device tree initialization is like this:
arm_mpam_device_probe() 	// driver probe
  mpam_discovery_start()	// start discover mpam devices
    [...] 			// find and add mpam devices
  mpam_discovery_complete()   	// trigger mpam_enable

When there are multiple mpam device nodes, the driver probe procedure
will execute more than once. However, the mpam_discovery_start() and
mpam_discovery_complete() should only run once. Besides, the start
should run first, and the complete should run after all devices added.

So we reorganize the device tree structure, so that there will be only
one mpam device parent nodes, and the probe procedure will only run once.
We add the child node to represent the mpam devices, and traverse and
add all mpam devices in the middle procedure of driver probe.

Signed-off-by: Xingang Wang <wangxingang5@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>