x86: Support Atom SoCs using SWSMISCI rather than the SWSCI

Some Atom SoCs use SWSMISCI for SMI control. Add a Kconfig to select this.
It is used on Apollo Lake.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 495629d..eddf2a7 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1017,4 +1017,10 @@
 	  network functionality. It is only here to generate the ACPI tables
 	  required by Linux.
 
+config INTEL_GMA_SWSMISCI
+	bool
+	help
+	  Select this option for Atom-based platforms which use the SWSMISCI
+	  register (0xe0) rather than the SWSCI register (0xe8).
+
 endmenu
diff --git a/arch/x86/cpu/apollolake/Kconfig b/arch/x86/cpu/apollolake/Kconfig
index 319f126..35a425c 100644
--- a/arch/x86/cpu/apollolake/Kconfig
+++ b/arch/x86/cpu/apollolake/Kconfig
@@ -17,6 +17,7 @@
 	select PCH_SUPPORT
 	select P2SB
 	select SMP_AP_WORK
+	select INTEL_GMA_SWSMISCI
 	select ACPI_GNVS_EXTERNAL
 	imply ENABLE_MRC_CACHE
 	imply AHCI_PCI