Bluetooth: df: Split CTE filtering SYNC_STAT_READY_OR_CONT_SCAN

The SYNC_STAT_READY_OR_CONT_SCAN state into two: SYNC_STAT_READY
and SYNC_STAT_CONT_SCAN. The connected state was used for two
cases:
- synchronization with periodic advertising is already established,
- CTE type is wrong but periodic advertising list is used to filter
synchronized devices.
In the past states were connected because there was only one difference
between them. In case of sync already established, Controller generated
sync report notification to host.The sync was not terminated when
Controller was about to continue search for other periodic advertiser.

The state was split because now Controller terminates sync ticker and
continues search for other periodic advertised. The split improves
readability and makes code easier to understand.

Signed-off-by: Piotr Pryga <piotr.pryga@nordicsemi.no>