[CPUFREQ] correct powernow-k8 fid/vid masks for extended parts

The fid/vid masks for parts using the extended parts are slightly incorrect and can result in
incorrect fid/vid codes being applied.  No instances of this problem have been reported in
the field but it could be a problem with future parts.

Signed-off-by: Mark Langsdorf <mark.langsdorf@amd.com>
Signed-off-by: Dave Jones <davej@redhat.com>