x86: add arch-specific SFI support

arch/x86/kernel/sfi.c serves the dual-purpose of supporting the
SFI core with arch specific code, as well as a home for the
arch-specific code that uses SFI.

analogous to ACPI, drivers/sfi/Kconfig is pulled in by arch/x86/Kconfig

Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Cc: x86@kernel.org
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 13ffa5d..d8ba424 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1683,6 +1683,8 @@
 
 source "drivers/acpi/Kconfig"
 
+source "drivers/sfi/Kconfig"
+
 config X86_APM_BOOT
 	bool
 	default y