Bluetooth: Fix requiring SMP MITM for outgoing connections

Due to recent changes to the way that the MITM requirement is set for
outgoing pairing attempts we can no longer rely on the hcon->auth_type
variable (which is actually good since it was formed from BR/EDR
concepts that don't really exist for SMP).

To match the logic that BR/EDR now uses simply rely on the local IO
capability and/or needed security level to set the MITM requirement for
outgoing pairing requests.

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