s390: fix /proc/interrupts output

The irqclass_sub_desc array and enum interruption_class are out of sync
thus /proc/interrupts is broken. Remove IRQIO_CLW.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>