Bluetooth: Fix sending wrong authentication requirements

Until we support any pairing method (Passkey Entry, OOB) that gives
MITM protection we shouldn't send that we have MITM protection.

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@openbossa.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>