Fix ptree having multiple roots

[dbenusov]

Problem solved by the commit

AIE partition json generation failed due to having multiple roots

Bug / issue (if any) fixed, which PR introduced the bug, how it was discovered

JSON output does not work

How problem was solved, alternative solutions (if any) and why they were rejected

Modified the tree to have one root

Risks (if any) associated the changes in the commit

None. This is a fix

What has been tested and how, request additional testing if necessary

Ubuntu 20.04

dbenusov@xsjdbenusov50:/proj/rdi/staff/dbenusov$ xbutil examine -d 17:00 -r aie-partitions -o test.json --force
***********************************************************
*        WARNING          WARNING          WARNING        *
*       SC version data missing. Upgrade your shell       *
***********************************************************

---------------------------------------------------
[0000:17:00.1] : xilinx_vck5000_gen4x8_qdma_base_2
---------------------------------------------------
AIE Partitions
  AIE Partition information unavailable

Successfully wrote the json file: test.json
dbenusov@xsjdbenusov50:/proj/rdi/staff/dbenusov$ echo $?
0
dbenusov@xsjdbenusov50:/proj/rdi/staff/dbenusov$ cat test.json
{
    "schema_version": {
        "schema": "JSON",
        "creation_date": "Tue Jul 11 22:42:29 2023 GMT"
    },
    "devices": [
        {
            "interface_type": "pcie",
            "device_id": "0000:17:00.1",
            "device_status": "HEALTHY",
            "aie_partitions": {
                "description": "AIE Partition Information",
                "partitions": ""
            }
        }
    ]
}

Documentation impact (if any)

None

[gbuildx]

Build Passed!