Bluetooth: Add support for Pairing features exchange

This patch implements a simple version of the SMP Pairing Features
exchange procedure (Vol. 3 Part H, Section 2.3.5.1).

For now, everything that would cause a Pairing Method different of
Just Works to be chosen is rejected.

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

net/bluetooth/hci_event.c

@@ -1622,6 +1622,7 @@ static inline void hci_encrypt_change_evt(struct hci_dev *hdev, struct sk_buff *
 				/* Encryption implies authentication */
 				conn->link_mode |= HCI_LM_AUTH;
 				conn->link_mode |= HCI_LM_ENCRYPT;
+				conn->sec_level = conn->pending_sec_level;
 			} else
 				conn->link_mode &= ~HCI_LM_ENCRYPT;
 		}