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/include/cpu/intel/speedstep.h

@@ -46,6 +46,9 @@
 #define MSR_THERM2_CTL    0x19D
 #define IA32_MISC_ENABLES 0x1A0
 #define MSR_FSB_CLOCK_VCC	0xce
+#define MSR_PMG_CST_CONFIG_CONTROL	0xe2
+#define MSR_PMG_IO_BASE_ADDR	0xe3
+#define MSR_PMG_IO_CAPTURE_ADDR	0xe4
 #define MSR_EXTENDED_CONFIG	0xee