crypto: remove bogus /= 2 for pbkdf iterations

When calculating iterations for pbkdf of the key slot
data, we had a /= 2, which was copied from identical
code in cryptsetup. It was always unclear & undocumented
why cryptsetup had this division and it was recently
removed there, too.
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

crypto/block-luks.c

@@ -1170,10 +1170,6 @@ qcrypto_block_luks_create(QCryptoBlock *block,
     /* iter_time was in millis, but count_iters reported for secs */
     iters = iters * luks_opts.iter_time / 1000;
 
-    /* Why /= 2 ?  That matches cryptsetup, but there's no
-     * explanation why they chose /= 2... */
-    iters /= 2;
-
     if (iters > UINT32_MAX) {
         error_setg_errno(errp, ERANGE,
                          "PBKDF iterations %llu larger than %u",