merge coreboot/u-boot download logic to one script

they are fundamentally the same, in an lbmk context.

they are downloaded in the same way, and compiled in
the same way!

(Kconfig infrastructure, board-specific code, the way
submodules are used in git, etc)

~200 sloc reduction in resources/scripts

the audit begins

Signed-off-by: Leah Rowe <leah@libreboot.org>

resources/scripts/update/blobs/inject

@@ -142,7 +142,7 @@ build_dependencies()
 {
 	if [ ! -d ${cbdir} ]; then
 		printf "downloading coreboot\n"
-		./download coreboot default
+		./fetch_trees coreboot default
 	fi
 
 	./build module cbutils default || fail "could not build cbutils"
@@ -200,7 +200,7 @@ patch_rom()
 
 	set -- "${boarddir}/config/"*
 	. ${1} 2>/dev/null
-	. "${boarddir}/board.cfg"
+	. "${boarddir}/target.cfg"
 
 	if [ "$CONFIG_HAVE_MRC" = "y" ]; then
 		inject_blob_intel_mrc "${rom}"