MFC r257769 to stable/10

Fix powerd/states on AMD cpus.  Resolves issues with system reporting:
hwpstate0: set freq failed, err 6

Tested on FX-8150 and others.

PR:		kern/167018
Submitted by:	avg@
Approved by:	re (gjb)

(cherry picked from commit 07f179266d161f0883f10fc89f19e9830e7f6ca3)

Requested by:

Ticket: #5719