x86: Issue SMI to finalize Coreboot in final stage

This will write magic value to APMC command port which
will trigger an SMI and cause coreboot to lock down
the ME, chipset, and CPU.

Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>

arch/x86/cpu/coreboot/coreboot.c

@@ -118,5 +118,9 @@ int board_final_cleanup(void)
 		enable_caches();
 	}
 
+	/* Issue SMI to Coreboot to lock down ME and registers */
+	printf("Finalizing Coreboot\n");
+	outb(0xcb, 0xb2);
+
 	return 0;
 }