cpu/amd: Add CC6 support

This patch adds CC6 power save support to the AMD Family 15h
support code.  As CC6 is a complex power saving state that
relies heavily on CPU, northbridge, and southbridge cooperation,
this patch alters significant amounts of code throughout the
tree simultaneously.

Allowing the CPU to enter CC6 allows the second level of turbo
boost to be reached, and also provides significant power savings
when the system is idle due to the complete core shutdown.

Change-Id: I44ce157cda97fb85f3e8f3d7262d4712b5410670
Signed-off-by: Timothy Pearson <tpearson@raptorengineeringinc.com>
Reviewed-on: http://review.coreboot.org/11979
Tested-by: build bot (Jenkins)
Tested-by: Raptor Engineering Automated Test Stand <noreply@raptorengineeringinc.com>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/include/cpu/amd/powernow.h

@@ -2,6 +2,7 @@
  * This file is part of the coreboot project.
  *
  * Copyright (C) 2009 Rudolf Marek <r.marek@assembler.cz>
+ * Copyright (C) 2015 Timothy Pearson <tpearson@raptorengineeringinc.com>, Raptor Engineering
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -17,5 +18,6 @@
 #define POWERNOW_H
 
 void amd_generate_powernow(u32 pcontrol_blk, u8 plen, u8 onlyBSP);
+void amd_powernow_update_fadt(acpi_fadt_t * fadt);
 
 #endif