trees: simplify copy_elf()

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

script/trees

@@ -291,11 +291,7 @@ mkpayload_grub()
 
 copy_elf()
 {
-	[ -f "$listfile" ] || return 0
-
-	x_ mkdir -p "$dest_dir"
-
-	while read -r f; do
+	[ -f "$listfile" ] && x_ mkdir -p "$dest_dir" && while read -r f; do
 		[ -f "$cdir/$f" ] && x_ cp "$cdir/$f" "$dest_dir"
 	done < "$listfile"
 	x_ make clean -C "$cdir"