x86: itss: Add a Kconfig option to enable/disable ITSS driver

Add a Kconfig option to support enabling/disabling the inclusion of
the ITSS driver depending on the platform.

Atuomatically select the ITSS driver when building for Apollo Lake.

Signed-off-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
[bmeng: squashed in http://patchwork.ozlabs.org/patch/1232761/]
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 89b93e5..b733d22 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -709,6 +709,12 @@
 	hex
 	default 0x10000
 
+config HAVE_ITSS
+	bool "Enable ITSS"
+	help
+	  Select this to include the driver for the Interrupt Timer
+	  Subsystem (ITSS) which is found on several Intel devices.
+
 menu "System tables"
 	depends on !EFI && !SYS_COREBOOT