avoid patch level msr on amd families < 0fh

avoid patch level msr on amd families < 0fh

Paul de Weerd reported it isn't implemented on ALIX with
cpu0: Geode(TM) Integrated Processor by AMD PCS ("AuthenticAMD" 586-class) 499 MHz, 05-0a-02

the earliest amd microcode update files I can find are for family 0fh (K8)

ok guenther@