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)
+{
+}