[S390] cio: Clean up messages.

- Remove unneeded messages.
- Move some messages into the debug feature.
- Use dev_* where appropriate.
- Use "cio: " prefix consistently.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>