[S390] dasd: fix timeout handling in interrupt handler

When the dasd_int_handler is called with an error code instead of
an irb, the associated request should be restarted. This handling
was missing from the -ETIMEDOUT case. In fact it should be done in
any case.

Signed-off-by: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>