!407 fix issues I4J4TK cat can not work well on big file

Merge pull request !407 from 冷钦街/cat_big2

components/shell/src/cmds/vfs_shellcmd.c

@@ -292,7 +292,7 @@ INT32 OsShellCmdCat(INT32 argc, const CHAR **argv)
         }
         PRINTK("%s", buf);
         (VOID)LOS_TaskDelay(1);
-    } while (size == CAT_BUF_SIZE);
+    } while (size == CAT_BUF_SIZE - 1);
 
     free(fullpath);
     close(fd);