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/include/cpu/cpu.h

@@ -9,10 +9,6 @@ struct bus;
 void initialize_cpus(struct bus *cpu_bus);
 void asmlinkage secondary_cpu_init(unsigned int cpu_index);
 
-void smm_init(void);
-void smm_lock(void);
-void smm_setup_structures(void *gnvs, void *tcg, void *smi1);
-
 #define __cpu_driver __attribute__ ((used,__section__(".rodata.cpu_driver")))
 #ifndef __SIMPLE_DEVICE__
 /** start of compile time generated pci driver array */