ipmi_fru_info_area: Fix Model Number name
ipmi_fru_info_area: Fix Model Number name

The FRU parser has always used the string `Model Number` for the IPMI
FRU property name. The change 45e93cbae0aa0d0f5385d40f5685b23e18f95351
broke reading this value since it stopped using the DBus property name
and switched to the FRU parser name.

Change-Id: Ie83f1a576680b7254f7858daacdc8803049b66f0
Signed-off-by: William A. Kennington III <30fff5198f4d10ca1117e5f3ec82f3b4b8900d81@google.com>

openbmc/phosphor-host-ipmid,openbmc/phosphor-host-ipmid,openbmc/phosphor-host-ipmid