X86: Introduce HW-Pstate scattered cpuid feature

It is rather similar to CPB (boot capability) feature
and exists since fam10h (can be looked up in AMD's BKDG).

The feature is needed for powernow-k8 to cleanup init functions and to
provide proper autoloading matching with the new x86cpu modalias
feature.

Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Dave Jones <davej@redhat.com>
Cc: Borislav Petkov <bp@amd64.org>
Signed-off-by: Thomas Renninger <trenn@suse.de>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>