x86: apl: Add systemagent driver

This driver handles communication with the systemagent which needs to be
told when U-Boot has completed its init.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/cpu/apollolake/Makefile b/arch/x86/cpu/apollolake/Makefile
index fdda748..3a8c2f6 100644
--- a/arch/x86/cpu/apollolake/Makefile
+++ b/arch/x86/cpu/apollolake/Makefile
@@ -2,5 +2,7 @@
 #
 # Copyright 2019 Google LLC
 
+obj-$(CONFIG_SPL_BUILD) += systemagent.o
+
 obj-y += pmc.o
 obj-y += uart.o