Populate MinimumVersion property

The Minimum Version is now an available D-Bus interface:
```
https://gerrit.openbmc.org/c/openbmc/phosphor-dbus-interfaces/+/70110
```
Populate its value if it's being defined.

Tested: If the msl meson options are defined, the D-Bus property is
populated with the value of the defined minimum version:
```
root@witherspoon:~# busctl get-property xyz.openbmc_project.Software.BMC.Updater /xyz/openbmc_project/software xyz.openbmc_project.Software.MinimumVersion MinimumVersion
s "2.15.0"
```

Change-Id: I0f9df0cfd7c06794df836e161b3416094a8535de
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
3 files changed