[S390] cio: Fix inverted isc priorities.

Priorities for I/O interruption subclasses range from 0 (highest)
to 7 (lowest). Unfortunately, the console has been using isc 7
instead of an isc with a higher priority than regular I/O
subchannels (which use 3). Fix this by making the console use
isc 1.

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