soc/intel/skylake: Add config option for Kabylake

Currently there is no distinction between mainboards using
Skylake or Kabylake SoC, Add a config option for Kabylake
SoC to allow mainboards to explicitly select if they are
using it.

Change-Id: Ie7960bd81f88a223894afe3115ddc0bc637e4be4
Signed-off-by: Rizwan Qureshi <rizwan.qureshi@intel.com>
Reviewed-on: https://review.coreboot.org/18312
Tested-by: build bot (Jenkins)
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Martin Roth <martinroth@google.com>

src/soc/intel/skylake/Kconfig

@@ -3,6 +3,13 @@ config SOC_INTEL_SKYLAKE
 	help
 	  Intel Skylake support
 
+config SOC_INTEL_KABYLAKE
+	bool
+	default n
+	select SOC_INTEL_SKYLAKE
+	help
+	  Intel Kabylake support
+
 if SOC_INTEL_SKYLAKE
 
 config CPU_SPECIFIC_OPTIONS