cpufreq: Linux support for the architectural pstate driver

cpufreq: Linux support for the architectural pstate driver

With the third generation Opteron parts, AMD switched to an
architecturally defined interface for PowerNow! that uses
different MSRs than previous versions.

This patch brings the PowerNow! driver up to match the mainline
Linux driver and provide support for all AMD parts that use
or will use the architectural pstate interface.

It also removes a WARN_ON statement in kernel/cpu.c that
highlights a cpu hotplug locking issue in the ondemand cpufreq
governor.  It is only a warning message and the scope of
the changes to properly surpress it is a bit large to add to
the Xen 2.6.18.8 kernel.  I will backport them if people
think that's a better idea.

Signed-off-by: Mark Langsdorf <mark.langsdorf@amd.com>