Bluetooth: hci_sync: Fix UAF on create_le_conn_complete

While waiting for hci_dev_lock the hci_conn object may be cleanup
causing the following trace:

BUG: KASAN: slab-use-after-free in hci_connect_le_scan_cleanup+0x29/0x350
Read of size 8 at addr ffff888001a50a30 by task kworker/u3:1/111

CPU: 0 PID: 111 Comm: kworker/u3:1 Not tainted
6.8.0-rc2-00701-g8179b15ab3fd-dirty #6418
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-1.fc38
04/01/2014
Workqueue: hci0 hci_cmd_sync_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x21/0x70
 print_report+0xce/0x620
 ? preempt_count_sub+0x13/0xc0
 ? __virt_addr_valid+0x15f/0x310
 ? hci_connect_le_scan_cleanup+0x29/0x350
 kasan_report+0xdf/0x110
 ? hci_connect_le_scan_cleanup+0x29/0x350
 hci_connect_le_scan_cleanup+0x29/0x350
 create_le_conn_complete+0x25c/0x2c0

Fixes: 881559af ("Bluetooth: hci_sync: Attempt to dequeue connection attempt")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>