[S390] cio: Deprecate read_dev_chars() and read_conf_data{,_lpm}().

These helper functions are a leftover from 2.4 sync I/O and are a
notorious source for bugs. They lead to device driver specific code
creeping into cio, and some issues can't really be fixed at all.

Device drivers can easily implement those functions themselves in a
more robust manner, so let's get rid of them.

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