s390/qdio: lock device while installing IRQ handler

During setup, qdio takes control of the presented ccw device and replaces
the device's IRQ handler with its own. To avoid any interference with
conccurent activity on the device, this should be done while holding the
device's lock.

Signed-off-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>