TPM code updater

This commit introduces a TPM code updater that currently supports
reading the firmware version for both Infineon and Nuvoton TPM 2.0.
Support for firmware updates will be introduced in a future patch.

The updater's configuration are managed by the EM [1].
[1] https://gerrit.openbmc.org/c/openbmc/entity-manager/+/82416

Tested on Yosemite5 with the following steps:

1. Display the fw inventory:
```
curl --silent $creds https://$bmc/redfish/v1/UpdateService/FirmwareInventory
{
  "@odata.id": "/redfish/v1/UpdateService/FirmwareInventory",
  "@odata.type": "#SoftwareInventoryCollection.SoftwareInventoryCollection",
  "Members": [
    {...},
    {
      "@odata.id": "/redfish/v1/UpdateService/FirmwareInventory/Yosemite5_TPM_4945"
    },
    {...}
  ],
  "Members@odata.count": 4,
  "Name": "Software Inventory Collection"
}
```

2. Query TPM version:
```
curl --silent $creds https://$bmc/redfish/v1/UpdateService/FirmwareInventory/Yosemite5_TPM_4945
{
  "@odata.id": "/redfish/v1/UpdateService/FirmwareInventory/Yosemite5_TPM_4945",
  "@odata.type": "#SoftwareInventory.v1_1_0.SoftwareInventory",
  "Description": "Unknown image",
  "Id": "Yosemite5_TPM_4945",
  "Name": "Software Inventory",
  "Status": {
    "Health": "Warning",
    "HealthRollup": "OK",
    "State": "Disabled"
  },
  "Updateable": false,
  "Version": "15.23"
}
```

Change-Id: I42568242356d55fe005ba1f41ddf8aaf9f682fc8
Signed-off-by: Kevin Tung <kevin.tung.openbmc@gmail.com>
diff --git a/tpm/xyz.openbmc_project.Software.TPM.service b/tpm/xyz.openbmc_project.Software.TPM.service
new file mode 100644
index 0000000..9598b91
--- /dev/null
+++ b/tpm/xyz.openbmc_project.Software.TPM.service
@@ -0,0 +1,13 @@
+[Unit]
+Description=TPM Device Code Update Daemon
+Requires=xyz.openbmc_project.EntityManager.service
+After=xyz.openbmc_project.EntityManager.service
+
+[Service]
+ExecStart=/usr/libexec/phosphor-code-mgmt/phosphor-tpm-software-update
+Restart=always
+Type=dbus
+BusName=xyz.openbmc_project.Software.TPM
+
+[Install]
+WantedBy=multi-user.target