[S390] cio: Catch operand exceptions on stsch.

If we have a subchannel id which has been generated via
for_each_subchannel(), it might contain an invalid subchannel set id.
We need to catch the ensuing operand exception by using stsch_err()
instead of stsch() in all possible cases.
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/cio/chsc.c

@@ -608,7 +608,7 @@ __chp_add_new_sch(struct subchannel_id schid)
 	struct schib schib;
 	int ret;
 
-	if (stsch(schid, &schib))
+	if (stsch_err(schid, &schib))
 		/* We're through */
 		return need_rescan ? -EAGAIN : -ENXIO;
 

drivers/s390/cio/css.c

@@ -296,7 +296,7 @@ static int css_evaluate_new_subchannel(struct subchannel_id schid, int slow)
 		/* Will be done on the slow path. */
 		return -EAGAIN;
 	}
-	if (stsch(schid, &schib) || !schib.pmcw.dnv) {
+	if (stsch_err(schid, &schib) || !schib.pmcw.dnv) {
 		/* Unusable - ignore. */
 		return 0;
 	}