Bluetooth: Fix MITM flag when initiating SMP pairing

The pairing process initiated through mgmt sets the conn->auth_type
value regardless of BR/EDR or LE pairing. This value will contain the
MITM flag if the local IO capability allows it. When sending the SMP
pairing request we should check the value and ensure that the MITM bit
gets correctly set in the bonding flags.

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