Minor - don't call smm_init() from init_bios_tables()

smm is a system feature, not a memory table.
diff --git a/src/smm.c b/src/smm.c
index 5a79269..07c2898 100644
--- a/src/smm.c
+++ b/src/smm.c
@@ -77,6 +77,9 @@
 void
 smm_init()
 {
+    if (CONFIG_COREBOOT)
+        // SMM only supported on emulators.
+        return;
     if (!CONFIG_USE_SMM)
         return;