cpupower: Remove family arg to decode_pstates()

The decode_pstates() routine no longer uses the CPU family and
the caleed routines (get_cof() and get_did()) can grab the family
from the global cpupower_cpu_info struct. These update removes
passing the family arg to all these routines.

Signed-off-by: Nathan Fontenot <nathan.fontenot@amd.com>
Reviewed-by: Robert Richter <rrichter@amd.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>