x86: Unify APERF/MPERF support

Initialize this CPUID flag feature in common code. It could be made a
standalone function later, maybe, if more functionality is duplicated.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
LKML-Reference: <1270065406-1814-4-git-send-email-bp@amd64.org>
Reviewed-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>