s390/cio: fix irq statistics

When we fetch an interrupt on the CCW console using tsch (via
ccw_device_wait_idle formerly known as wait_cons_dev) we increment
the irq count for the affected interruption class but it is not
accounted as an IO interrupt.

This is broken since commit b603d258
"s390: remove superfluous tpi from wait_cons_dev"

Fix it so that the sum of the individual interrupts per class matches
the number of IO interrupts again.

Reported-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>