fsp2_0: Clean up around config FSP_USE_REPO

We can make our lifes much easier by removing its dependency on
`ADD_FSP_BINARIES`. Instead, we imply the latter if the repository
is to be used. We can also hide a lot of unnecessary prompts in
this case.

Also, remove default overrides and selects for the two that are
now unnecessary.

Change-Id: I8538f2e966adc9da0fbea2250c954d86e42dfeb3
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39882
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by:  Felix Singer <felixsinger@posteo.net>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

util/abuild/abuild

@@ -720,7 +720,7 @@ while true ; do
 			shift;;
 		-B|--blobs)	shift
 			customizing="${customizing}, blobs"
-			configoptions="${configoptions}CONFIG_USE_BLOBS=y\nCONFIG_USE_AMD_BLOBS=y\nCONFIG_ADD_FSP_BINARIES=y\nCONFIG_FSP_USE_REPO=y\n"
+			configoptions="${configoptions}CONFIG_USE_BLOBS=y\nCONFIG_USE_AMD_BLOBS=y\nCONFIG_ADD_FSP_BINARIES=y\n"
 			;;
 		-A|--any-toolchain)	shift
 			customizing="${customizing}, any-toolchain"