This attempts to avoid circular locking dependency between sock_lock
and hdev_lock:

WARNING: possible circular locking dependency detected
6.0.0-rc7-03728-g18dd8ab0a783 #3 Not tainted
------------------------------------------------------
kworker/u3:2/53 is trying to acquire lock:
ffff888000254130 (sk_lock-AF_BLUETOOTH-BTPROTO_ISO){+.+.}-{0:0}, at:
iso_conn_del+0xbd/0x1d0
but task is already holding lock:
ffffffff9f39a080 (hci_cb_list_lock){+.+.}-{3:3}, at:
hci_le_cis_estabilished_evt+0x1b5/0x500
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (hci_cb_list_lock){+.+.}-{3:3}:
       __mutex_lock+0x10e/0xfe0
       hci_le_remote_feat_complete_evt+0x17f/0x320
       hci_event_packet+0x39c/0x7d0
       hci_rx_work+0x2bf/0x950
       process_one_work+0x569/0x980
       worker_thread+0x2a3/0x6f0
       kthread+0x153/0x180
       ret_from_fork+0x22/0x30
-> #1 (&hdev->lock){+.+.}-{3:3}:
       __mutex_lock+0x10e/0xfe0
       iso_connect_cis+0x6f/0x5a0
       iso_sock_connect+0x1af/0x710
       __sys_connect+0x17e/0x1b0
       __x64_sys_connect+0x37/0x50
       do_syscall_64+0x43/0x90
       entry_SYSCALL_64_after_hwframe+0x62/0xcc
-> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_ISO){+.+.}-{0:0}:
       __lock_acquire+0x1b51/0x33d0
       lock_acquire+0x16f/0x3b0
       lock_sock_nested+0x32/0x80
       iso_conn_del+0xbd/0x1d0
       iso_connect_cfm+0x226/0x680
       hci_le_cis_estabilished_evt+0x1ed/0x500
       hci_event_packet+0x39c/0x7d0
       hci_rx_work+0x2bf/0x950
       process_one_work+0x569/0x980
       worker_thread+0x2a3/0x6f0
       kthread+0x153/0x180
       ret_from_fork+0x22/0x30
other info that might help us debug this:
Chain exists of:
  sk_lock-AF_BLUETOOTH-BTPROTO_ISO --> &hdev->lock --> hci_cb_list_lock
 Possible unsafe locking scenario:
       CPU0                    CPU1
       ----                    ----
  lock(hci_cb_list_lock);
                               lock(&hdev->lock);
                               lock(hci_cb_list_lock);
  lock(sk_lock-AF_BLUETOOTH-BTPROTO_ISO);
 *** DEADLOCK ***
4 locks held by kworker/u3:2/53:
 #0: ffff8880021d9130 ((wq_completion)hci0#2){+.+.}-{0:0}, at:
 process_one_work+0x4ad/0x980
 #1: ffff888002387de0 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0},
 at: process_one_work+0x4ad/0x980
 #2: ffff888001ac0070 (&hdev->lock){+.+.}-{3:3}, at:
 hci_le_cis_estabilished_evt+0xc3/0x500
 #3: ffffffff9f39a080 (hci_cb_list_lock){+.+.}-{3:3}, at:
 hci_le_cis_estabilished_evt+0x1b5/0x500
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>