src/*/intel: introduce warning when building with no IFD

Add a warning as suggested in patch CB:28233 with the
"CONFIG_INTEL_DESCRIPTOR_MODE_REQUIRED" option.

Change-Id: I42b6b336bb519f3d18b5a41eb20b380636ff5819
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/28382
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
diff --git a/src/southbridge/intel/i82801jx/Kconfig b/src/southbridge/intel/i82801jx/Kconfig
index bf2d01f..cb5b12f 100644
--- a/src/southbridge/intel/i82801jx/Kconfig
+++ b/src/southbridge/intel/i82801jx/Kconfig
@@ -36,6 +36,11 @@
 	hex
 	default 0xfef00000
 
+## Some enterprise variants may require an IFD
+config INTEL_DESCRIPTOR_MODE_REQUIRED
+	bool
+	default n
+
 config HPET_MIN_TICKS
 	hex
 	default 0x80