Bluetooth: L2CAP: Fix deadlock in l2cap_conn_del()

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: L2CAP: Fix deadlock in l2cap_conn_del()

l2cap_conn_del() calls cancel_delayed_work_sync() for both info_timer

and id_addr_timer while holding conn->lock. However, the work functions

l2cap_info_timeout() and l2cap_conn_update_id_addr() both acquire

conn->lock, creating a potential AB-BA deadlock if the work is already

executing when l2cap_conn_del() takes the lock.

Move the work cancellations before acquiring conn->lock and use

disable_delayed_work_sync() to additionally prevent the works from

being rearmed after cancellation, consistent with the pattern used in

hci_conn_del().