i82801dx/gx/ix/jx: Add low-memory backup for S3 path

SMM relocation code overwrite low memory owned by OS.

Change-Id: Ifa3d28bed3d3db65b0707bde62ae2b424a231f1a
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/19405
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/cpu/x86/lapic/lapic_cpu_init.c

@@ -587,6 +587,8 @@ void initialize_cpus(struct bus *cpu_bus)
 		}
 	}
 
+	smm_init_completion();
+
 	if (is_smp_boot())
 		recover_lowest_1M();
 }
@@ -595,3 +597,7 @@ void initialize_cpus(struct bus *cpu_bus)
 __attribute__((weak)) void smm_init(void)
 {
 }
+
+__attribute__((weak)) void smm_init_completion(void)
+{
+}