build: it is no longer necessary to call make target/linux/clean as part of make clean

SVN-Revision: 34451

Makefile

@@ -54,7 +54,6 @@ printdb:
 prepare: $(target/stamp-compile)
 
 clean: FORCE
-	$(_SINGLE)$(SUBMAKE) target/linux/clean
 	rm -rf $(BUILD_DIR) $(BIN_DIR) $(BUILD_LOG_DIR)
 
 dirclean: clean