Fix off-by-one error in maximum keyfile size.
Fix off-by-one error in maximum keyfile size.

Allow keyfiles up to DEFAULT_KEYFILE_SIZE_MAXKB * 1024 bytes in size, and not that value minus one.

Signed-off-by: Vittorio Gambaletta <08adaabf44956491ba6b908126d07947cd773893@vittgam.net>
periodic1236/cryptsetup,periodic1236/cryptsetup,periodic1236/cryptsetup