fs/ntfs3: Prevent integer overflow in hdr_first_de()

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.

Fixes: 60ce8dfde035 ("fs/ntfs3: Fix wrong if in hdr_first_de")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>