Bluetooth: Remove dead code from SMP encryption function

The AES cipher is used in ECB mode by SMP and therefore doesn't use an
IV (crypto_blkcipher_ivsize returns 0) so the code trying to set the IV
was never getting called. Simply remove this code to avoid anyone from
thinking it actually makes some difference.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>