[S390] cio: Export some symbols for modular css drivers.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c
index cf9d27c..bc3a8e4 100644
--- a/drivers/s390/cio/css.c
+++ b/drivers/s390/cio/css.c
@@ -158,12 +158,17 @@
 	return ret;
 }
 
+/**
+ * css_sch_device_unregister - unregister a subchannel
+ * @sch: subchannel to be unregistered
+ */
 void css_sch_device_unregister(struct subchannel *sch)
 {
 	mutex_lock(&sch->reg_mutex);
 	device_unregister(&sch->dev);
 	mutex_unlock(&sch->reg_mutex);
 }
+EXPORT_SYMBOL_GPL(css_sch_device_unregister);
 
 static void ssd_from_pmcw(struct chsc_ssd_info *ssd, struct pmcw *pmcw)
 {