x86: apl: Check low-level init in FSP-S pre-init

If U-Boot is not running FSP-S it should not do the pre-init either. Add a
condition to handle this.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/cpu/apollolake/fsp_s.c b/arch/x86/cpu/apollolake/fsp_s.c
index e54b0ac..715ceab 100644
--- a/arch/x86/cpu/apollolake/fsp_s.c
+++ b/arch/x86/cpu/apollolake/fsp_s.c
@@ -157,6 +157,8 @@
 	struct udevice *itss;
 	int ret;
 
+	if (!ll_boot_init())
+		return 0;
 	ret = irq_first_device_type(X86_IRQT_ITSS, &itss);
 	if (ret)
 		return log_msg_ret("no itss", ret);