AMD: Drop six copies of wrmsr_amd and rdmsr_amd

Based on comments in cpu/x86/msr.h for wrmsr/rdmsr, and for symmetry,
I have added __attribute__((always_inline)) for these.

Change-Id: Ia0a34c15241f9fbc8c78763386028ddcbe6690b1
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/2898
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Marc Jones <marc.jones@se-eng.com>

src/cpu/x86/mtrr/earlymtrr.c

@@ -2,8 +2,8 @@
 #define EARLYMTRR_C
 #include <cpu/x86/cache.h>
 #include <cpu/x86/mtrr.h>
-#include <cpu/amd/mtrr.h>
 #include <cpu/x86/msr.h>
+#include <cpu/amd/mtrr.h>
 
 static void set_var_mtrr(
 	unsigned reg, unsigned base, unsigned size, unsigned type)