put coreboot utils in elf/, not cbutils/

one directory per util, under elf/

e.g. elf/cbfstool/

further split by tree name, e.g.:

elf/cbfstool/default/
elf/cbfstool/foo/

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

script/roms

@@ -209,7 +209,7 @@ build_payloads()
 	romdir="bin/$board"
 	cbdir="src/coreboot/$board"
 	[ "$board" = "$tree" ] || cbdir="src/coreboot/$tree"
-	cbfstool="cbutils/$tree/cbfstool"
+	cbfstool="elf/cbfstool/$tree/cbfstool"
 	cbrom="$cbdir/build/coreboot.rom"
 
 	[ -f "$cbfstool" ] || x_ ./update trees -b coreboot utils $tree