arch/x86: Sanity checking on HAVE_SMI_HANDLER

Fail at build-time if one of the following happens:

Platform includes SMI handler setup function smm_init()
in the build when configuration has HAVE_SMI_HANDLER=n.

Platform does not implement smm_init_completion() when
HAVE_SMI_HANDLER=y.

Change-Id: I7d61c155d2b7c2d71987980db4c25d520452dabf
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/21097
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/cpu/amd/smm/smm_init.c

@@ -77,3 +77,7 @@ void smm_lock(void)
 {
 	/* We lock SMM in CPU init */
 }
+
+void smm_init_completion(void)
+{
+}

src/cpu/x86/lapic/lapic_cpu_init.c

@@ -593,11 +593,13 @@ void initialize_cpus(struct bus *cpu_bus)
 		recover_lowest_1M();
 }
 
-/* Platform-specific code for SMI handler overrides this. */
+#if !IS_ENABLED(CONFIG_HAVE_SMI_HANDLER)
-__attribute__((weak)) void smm_init(void)
+/* Empty stubs for platforms without SMI handlers. */
+void smm_init(void)
 {
 }
 
-__attribute__((weak)) void smm_init_completion(void)
+void smm_init_completion(void)
 {
 }
+#endif

src/soc/intel/sch/smi.c

@@ -312,6 +312,10 @@ void smm_init(void)
 	smi_set_eos();
 }
 
+void smm_init_completion(void)
+{
+}
+
 void smm_lock(void)
 {
 	/* LOCK the SMM memory window and enable normal SMM.