Bluetooth: Fix sec_level

We should set conn->pending_sec_level in hci_le_ltk_request_evt,
otherwise conn->sec_level is not properly updated once we get an
Encryption Change Event.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Bluetooth: Fix key size

We should set conn->enc_key_size in hci_le_ltk_request_evt, otherwise
it is left unitialized.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>