speedstep: Deduplicate some MSR identifiers

In particular:
MSR_PMG_CST_CONFIG_CONTROL
MSR_PMG_IO_BASE_ADDR
MSR_PMG_IO_CAPTURE_ADDR

Change-Id: Ief2697312f0edf8c45f7d3550a7bedaff1b69dc6
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/2337
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/cpu/intel/model_206ax/finalize.c

@@ -22,6 +22,7 @@
 #include <stdlib.h>
 #include <cpu/cpu.h>
 #include <cpu/x86/msr.h>
+#include <cpu/intel/speedstep.h>
 #include "model_206ax.h"
 
 static void msr_set_bit(unsigned reg, unsigned bit)