cpu: Add support for part and serial numbers

This will obtain the part and serial numbers from SMBIOS, and store
them in the cpu dbus interface. The serial number is obtained from
the Serial Number Offset of 20h, and the part number is obtained
from the Part Number Offset of 22h.

Tested:
 - Both dbus and Redfish present the part and serial numbers
   obtained from SMBIOS.

Signed-off-by: Charles Boyer <Charles.Boyer@fii-usa.com>
Change-Id: I5b26ed5c0ce1135aa7aba3e335ec7da1588d11b1
2 files changed