x86: Add multi-processor init

Most modern x86 CPUs include more than one CPU core. The OS normally requires
that these 'Application Processors' (APs) be brought up by the boot loader.
Add the required support to U-Boot to init additional APs.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/cpu/ivybridge/model_206ax.c b/arch/x86/cpu/ivybridge/model_206ax.c
index 11dc625..8b08c40 100644
--- a/arch/x86/cpu/ivybridge/model_206ax.c
+++ b/arch/x86/cpu/ivybridge/model_206ax.c
@@ -435,8 +435,8 @@
 
 		debug("CPU: %u has core %u\n", cpu->apic_id, new_cpu->apic_id);
 
-#if CONFIG_SMP && CONFIG_MAX_CPUS > 1
-		/* Start the new cpu */
+#if 0 && CONFIG_SMP && CONFIG_MAX_CPUS > 1
+		/* TODO(sjg@chromium.org): Start the new cpu */
 		if (!start_cpu(new_cpu)) {
 			/* Record the error in cpu? */
 			printk(BIOS_ERR, "CPU %u would not start!\n",