cpupower: Update msr_pstate union struct naming

cpupower: Update msr_pstate union struct naming

The msr_pstate union struct named fam17h_bits is misleading since
this is the struct to use for all families >= 0x17, not just
for family 0x17. Rename the bits structs to be 'pstate' (for pre
family 17h CPUs) and 'pstatedef' (for CPUs since fam 17h) to align
closer with PPR/BDKG (1) naming.

There are no functional changes as part of this update.

1: AMD Processor Programming Reference (PPR) and BIOS and
Kernel Developer's Guide (BKDG) available at:
http://developer.amd.com/resources/developer-guides-manuals

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