Bluetooth: Use list_for_each_entry_rcu() to traverse RCU list in RCU read-side CS

In function hci_is_blocked_key() RCU list is traversed with
list_for_each_entry() in RCU read-side CS.
Use list_for_each_entry_rcu() instead.

Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>