Add proper cpu scaling support for amd cpus

[Andrew Berg]

On 2013.12.03 13:35, Claudio wrote:
> Hello,
> 
> Would it be possible to apply this patch: http://www.freebsd.org/cgi/query-pr.cgi?pr=167018 to stable so that it gets in 10 release? without it cpu scaling on most (especially recent) amd cpus doesn't work properly and the dmesg gets cluttered with "hwpstate0: set freq failed " errors.
I'd like to see this as well since the spam makes it impossible to get anything useful from dmesg after a while.