fsp2_0: Gather Kconfig declarations

Move more Kconfig declarations to drivers/intel/fsp2_0/ and document
them properly. This way, we don't have to repeat dependencies and have
the prompts in a common place. We can also easily hide the prompt for
the header path in case the FSP repository is used.

SP platforms were skipped as their Kconfig is too weird but they
shouldn't hold other platforms back.

Change-Id: Iba5af49bcd15427e9eb9b111e6c4cc9bcb7adcae
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40125
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by:  Felix Singer <felixsinger@posteo.net>

src/soc/intel/skylake/Kconfig

@@ -222,14 +222,11 @@ config NHLT_DA7219
 	  Include DSP firmware settings for DA7219 headset codec.
 
 config FSP_HEADER_PATH
-	string "Location of FSP headers"
 	# Use KabylakeFsp for both Skylake and Kabylake as it supports both.
 	# SkylakeFsp is FSP 1.1 and therefore incompatible.
 	default "3rdparty/fsp/KabylakeFspBinPkg/Include/"
 
 config FSP_FD_PATH
-	string
-	depends on FSP_USE_REPO
 	default "3rdparty/fsp/KabylakeFspBinPkg/Fsp.fd"
 
 config MAX_ROOT_PORTS