x86: apl: Add ITSS driver

This driver models some sort of interrupt thingy but there are so many
abreviations that I cannot find out what it stands for. Possibly something
to do with interrupts.

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 4d3c08f..2d78368 100644
--- a/arch/x86/cpu/apollolake/Makefile
+++ b/arch/x86/cpu/apollolake/Makefile
@@ -5,5 +5,6 @@
 obj-$(CONFIG_SPL_BUILD) += systemagent.o
 
 obj-y += hostbridge.o
+obj-y += itss.o
 obj-y += pmc.o
 obj-y += uart.o