nvidia-gpu: add support for ConnectX device

Add support to discover ConnectX devices and to populate PCIe interface
properties using Phosphor DBus Interface
xyz.openbmc_project.Inventory.Item.PCIeDe

nvidia-gpu: add support for ConnectX device

Add support to discover ConnectX devices and to populate PCIe interface
properties using Phosphor DBus Interface
xyz.openbmc_project.Inventory.Item.PCIeDevice.

ConnectX device has an integrated PCIe Switch. The patch uses
xyz.openbmc_project.Inventory.Item.PCIeSwitch PDI to define the PCIe
Switch resource.

Tested: Build an image for nvl32-obmc machine with the following patch
cherry picked.

https://gerrit.openbmc.org/c/openbmc/openbmc/+/85490

The patch cherry-picks the following patches that are currently under
review.

```
1. device tree
https://lore.kernel.org/all/aRbLqH8pLWCQryhu@molberding.nvidia.com/
2. mctpd patches
https://github.com/CodeConstruct/mctp/pull/85
3. u-boot changes
https://lore.kernel.org/openbmc/20251121-msx4-v1-0-fc0118b666c1@nvidia.com/T/#t
4. kernel changes as specified in the openbmc patch (for espi)
5. entity-manager changes
https://gerrit.openbmc.org/c/openbmc/entity-manager/+/85455
6. platform-init changes
https://gerrit.openbmc.org/c/openbmc/platform-init/+/85456
7. spi changes
https://lore.kernel.org/all/20251121-w25q01jv_fixup-v1-1-3d175050db73@nvidia.com/
```

```
root@nvl32-bmc:~# busctl tree xyz.openbmc_project.GpuSensor
`- /xyz
`- /xyz/openbmc_project
|- /xyz/openbmc_project/inventory
| `- /xyz/openbmc_project/inventory/pcie_devices
| |- /xyz/openbmc_project/inventory/pcie_devices/Nvidia_ConnectX_0
| |- /xyz/openbmc_project/inventory/pcie_devices/Nvidia_ConnectX_1
| |- /xyz/openbmc_project/inventory/pcie_devices/Nvidia_ConnectX_2
| `- /xyz/openbmc_project/inventory/pcie_devices/Nvidia_ConnectX_3

root@nvl32-obmc:~# busctl introspect xyz.openbmc_project.GpuSensor /xyz/openbmc_project/inventory/pcie_devices/Nvidia_ConnectX_0
NAME TYPE SIGNATURE RESULT/VALUE FLAGS
org.freedesktop.DBus.Introspectable interface - - -
.Introspect method - s -
org.freedesktop.DBus.Peer interface - - -
.GetMachineId method - s -
.Ping method - - -
org.freedesktop.DBus.Properties interface - - -
.Get method ss v -
.GetAll method s a{sv} -
.Set method ssv - -
.PropertiesChanged signal sa{sv}as - -
xyz.openbmc_project.Inventory.Item.PCIeDevice interface - - -
.GenerationInUse property s "xyz.openbmc_project.Inventory.Item.P... emits-change
.GenerationSupported property s "xyz.openbmc_project.Inventory.Item.P... emits-change
.LanesInUse property u 8 emits-change
.MaxLanes property u 16 emits-change
xyz.openbmc_project.Inventory.Item.PCIeSwitch interface - - -

$ curl -s -k -u 'root:0penBmc' https://${bmc_ip}/redfish/v1/Systems/system/PCIeDevices/Nvidia_ConnectX_0
{
"@odata.id": "/redfish/v1/Systems/system/PCIeDevices/Nvidia_ConnectX_0",
"@odata.type": "#PCIeDevice.v1_19_0.PCIeDevice",
"Id": "Nvidia_ConnectX_0",
"Name": "PCIe Device",
"PCIeFunctions": {
"@odata.id": "/redfish/v1/Systems/system/PCIeDevices/Nvidia_ConnectX_0/PCIeFunctions"
},
"PCIeInterface": {
"LanesInUse": 8,
"MaxLanes": 16,
"MaxPCIeType": "Gen5",
"PCIeType": "Gen5"
},
"Status": {
"Health": "OK",
"State": "Enabled"
}
}%
```

Change-Id: Id89ce8a298ebb16934e94efcb9ca4679f91a7b26
Signed-off-by: Harshit Aghera <haghera@nvidia.com>

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