lbmk: don't use status for unconditional returns

in cases where lbmk must always return from a function,
there are some cases where it relies on non-zero exit
status, which in practise is always the case, but may
change in the future if the relevant part is modified

e.g. do_something && return 0

the proper form is:
do_something
return 0

also do this for unconditional exits

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

script/vendor/inject

@@ -14,8 +14,10 @@ eval "$(setvars "" archive rom modifygbe nukemode release new_mac)"
 main()
 {
 	[ $# -lt 1 ] && err "No options specified."
-	[ "${1}" = "listboards" ] && \
-		items config/coreboot && exit 0
+	if [ "${1}" = "listboards" ]; then
+		items config/coreboot || :
+		exit 0
+	fi
 
 	archive="${1}"