x86: Add SMM helper functions to MP infrastructure

In order for the cpu code to start SMM relocation 2 new
functions are added to be shared:
- void smm_initiate_relocation_parallel()
- void smm_initiate_relocation()
The both initiate an SMI on the currently running cpu.
The 2 variants allow for parallel relocation or serialized
relocation.

BUG=chrome-os-partner:22862
BRANCH=None
TEST=Built and booted rambi using these functions.

Change-Id: I325777bac27e9a0efc3f54f7223c38310604c5a2
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/173982
Reviewed-on: http://review.coreboot.org/4891
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Tested-by: build bot (Jenkins)

src/include/cpu/x86/mp.h

@@ -117,4 +117,13 @@ void mp_initialize_cpu(void *unused);
 /* Returns apic id for coreboot cpu number or < 0 on failure. */
 int mp_get_apic_id(int cpu_slot);
 
+/*
+ * SMM helpers to use with initializing CPUs.
+ */
+
+/* Send SMI to self without any serialization. */
+void smm_initiate_relocation_parallel(void);
+/* Send SMI to self with single execution. */
+void smm_initiate_relocation(void);
+
 #endif /* _X86_MP_H_ */