Update submodule check to include LUFA (#6661)

As LUFA is now a submodule, we should be checking it.

Makefile

@@ -548,6 +548,7 @@ ifndef SKIP_GIT
 	if [ ! -e lib/chibios ]; then git submodule sync lib/chibios && git submodule update --depth 1 --init lib/chibios; fi
 	if [ ! -e lib/chibios-contrib ]; then git submodule sync lib/chibios-contrib && git submodule update --depth 1 --init lib/chibios-contrib; fi
 	if [ ! -e lib/ugfx ]; then git submodule sync lib/ugfx && git submodule update --depth 1 --init lib/ugfx; fi
+	if [ ! -e lib/lufa ]; then git submodule sync lib/lufa && git submodule update --depth 1 --init lib/lufa; fi
 	git submodule status --recursive 2>/dev/null | \
 	while IFS= read -r x; do \
 		case "$$x" in \