bluetooth: hci_conn: fix LE connections when size is exactly 56 bits

* fixes dev-harsh1998/kernel_lenovo_msm8916@5d6a681eb503d2d151c07b8a66db45b62d4c9170
* based on history of changes https://github.com/torvalds/linux/blob/master/net/bluetooth/hci_conn.c#L1263



Signed-off-by: dev-harsh1998 <dev-harsh1998@hotmail.com>