CPU: Move SMM prototypes under x86

Change-Id: Iefbc17dcfcf312338d94b2c2945c7fac3b23bff6
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/17732
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)

src/arch/x86/include/arch/cpu.h

@@ -163,6 +163,10 @@ int cpu_cpuid_extended_level(void);
 int cpu_have_cpuid(void);
 int cpu_phys_address_size(void);
 
+void smm_init(void);
+void smm_lock(void);
+void smm_setup_structures(void *gnvs, void *tcg, void *smi1);
+
 #ifndef __SIMPLE_DEVICE__
 
 struct device;