Bluetooth: hci_sync: Avoid use-after-free in dbg for hci_add_adv_monitor()

KSAN reports use-after-free in hci_add_adv_monitor().

While adding an adv monitor,
    hci_add_adv_monitor() calls ->
    msft_add_monitor_pattern() calls ->
    msft_add_monitor_sync() calls ->
    msft_le_monitor_advertisement_cb() calls in an error case ->
    hci_free_adv_monitor() which frees the *moniter.

This is referenced by bt_dev_dbg() in hci_add_adv_monitor().

Fix the bt_dev_dbg() by using handle instead of monitor->handle.

Fixes: b747a836

 ("Bluetooth: hci_sync: Refactor add Adv Monitor")
Signed-off-by: Manish Mandlik <mmandlik@google.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>