s390/cio: fix irq stats for early interrupts on ccw consoles

Interrupts which happen on ccw consoles prior to their registration
with the driver core are not accounted to the respective device
driver. Fix this by setting the proper interrupt class during
initialization of ccw consoles.

Reviewed-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>