Bluetooth: hci_event: Fix sending HCI_OP_READ_ENC_KEY_SIZE

The code shall always check if HCI_QUIRK_BROKEN_READ_ENC_KEY_SIZE has
been set before attempting to use HCI_OP_READ_ENC_KEY_SIZE.

Fixes: c569242c

 ("Bluetooth: hci_event: set the conn encrypted before conn establishes")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>