[S390] cio: fix orb initialization in cio_start_key

The functions cio_tm_start_key and cio_start_key use the same private
orb structure of a subchannel, so the orb needs to be cleared of old
data before it is used again. A respective memset is missing from
cio_start_key and hereby added.
Signed-off-by: Stefan Weinhuber <wein@de.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/cio/cio.c

@@ -174,6 +174,7 @@ cio_start_key (struct subchannel *sch,	/* subchannel structure */
 	CIO_TRACE_EVENT(4, sch->dev.bus_id);
 
 	orb = &to_io_private(sch)->orb;
+	memset(orb, 0, sizeof(union orb));
 	/* sch is always under 2G. */
 	orb->cmd.intparm = (u32)(addr_t)sch;
 	orb->cmd.fmt = 1;