intel/fsp2_0: Make FSP_USE_REPO a SoC opt-in

For quite a bit now we are extending the FSP_USE_REPO option to be
available for all Intel SoCs. This results in a list being not only
hard to maintain but also prone to errors.

To change that behaviour this commit introduces the
HAVE_INTEL_FSP_REPO config option for SoCs that are supported from within
3rdparty/fsp.

If a SoC selects HAVE_INTEL_FSP_REPO the config option FSP_USE_REPO is
selected by default, but can be still deselected by the user in menuconfig.

Change-Id: I68ae373ce591f06073064aa75aac32ceca8fa1cc
Signed-off-by: Johanna Schander <coreboot@mimoja.de>
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37582
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/skylake/Kconfig

@@ -39,6 +39,7 @@ config CPU_SPECIFIC_OPTIONS
 	select INTEL_CAR_NEM_ENHANCED
 	select INTEL_GMA_ACPI
 	select INTEL_GMA_ADD_VBT if RUN_FSP_GOP
+	select HAVE_INTEL_FSP_REPO
 	select IOAPIC
 	select MRC_SETTINGS_PROTECT
 	select PARALLEL_MP