Bluetooth: use memset avoid memory leaks

Similar to the handling of l2cap_ecred_connect in commit d3715b23


("Bluetooth: use memset avoid memory leaks"), we thought a patch
might be needed here as well.

Use memset to initialize structs to prevent memory leaks
in l2cap_le_connect

Signed-off-by: Xiaohui Zhang <xiaohuizhang@ruc.edu.cn>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>