fs/ntfs3: Prevent integer overflow in hdr_first_de()

In the Linux kernel, the following vulnerability has been resolved: fs/ntfs3: Prevent integer overflow in hdr_first_de() The "de_off" and "used" variables come from the disk so they both need to check. The problem is that on 32bit systems if they're both greater than UINT_MAX - 16 then the check does work as intended because of an integer overflow.