soc/intel/cnl: Add new Kconfig option which matches its FSPs name

Since there are 4 different versions of FSPs for the Comet Lake
platform, add a new Kconfig option for the currently used SoC being able
to differ between the various SoCs and FSPs.

The new Kconfig option selects the Comet Lake SoC as base for taking
over its specific configuration and is only used for configuring the
path to its specific FSP header files and FSP binary.

Also, adjust all related mainboards so that their Kconfig selects the
new option.

For details, please see
https://github.com/intel/FSP/tree/master/CometLakeFspBinPkg

Built System76/lemp9 with BUILD_TIMELESS=1 before and after this patch
and both images are equal.

Change-Id: I44b717bb942fbcd359c7a06ef1a0ef4306697f64
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44952
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Michael Niewöhner

src/mainboard/intel/coffeelake_rvp/Kconfig.name

@@ -14,4 +14,4 @@ config BOARD_INTEL_COFFEELAKE_RVP8
 	select SOC_INTEL_COFFEELAKE
 config BOARD_INTEL_COMETLAKE_RVPU
 	bool "-> Cometlake U DDR4 RVP"
-	select SOC_INTEL_COMETLAKE
+	select SOC_INTEL_COMETLAKE_1