soc/intel/skylake: Clean up Kconfig

This does the following:
- select MAINBOARD_USES_FSP2_0 on Kabylake (does not support FSP1.1)
- Remove stale Kconfig option on intel/saddlebrook
- select SOC_INTEL_KABYLAKE on intel/kblrvp

Change-Id: I64f48eeb00150aea039d533b0ac471fdd8483b90
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/33561
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/soc/intel/skylake/Kconfig

@@ -1,16 +1,20 @@
+config SOC_INTEL_COMMON_SKYLAKE_BASE
+	bool
+
 config SOC_INTEL_SKYLAKE
 	bool
+	select SOC_INTEL_COMMON_SKYLAKE_BASE
 	help
 	  Intel Skylake support
 
 config SOC_INTEL_KABYLAKE
 	bool
-	default n
-	select SOC_INTEL_SKYLAKE
+	select SOC_INTEL_COMMON_SKYLAKE_BASE
+	select MAINBOARD_USES_FSP2_0
 	help
 	  Intel Kabylake support
 
-if SOC_INTEL_SKYLAKE
+if SOC_INTEL_COMMON_SKYLAKE_BASE
 
 config CPU_SPECIFIC_OPTIONS
 	def_bool y