Bluetooth: CSIP: Fix ntf issue to clients on reboot

On reboot, client list to notify is not updated properly.
Fix is to check and add the reconnected clients on
security changed cb.

Subscription check is added before notify to clients.
BT Enable check is added in the register function before adding
bonded devices to client list.

Also typo is corrected in add_bonded_addr_to_client_list in the
second loop.

Signed-off-by: Nithin Ramesh Myliattil <niym@demant.com>