s390/cio: export hsch to modules

The vfio-ccw code will need this, and it matches treatment of ssch
and csch.
Reviewed-by: NPierre Morel <pmorel@linux.ibm.com>
Reviewed-by: NHalil Pasic <pasic@linux.ibm.com>
Signed-off-by: NCornelia Huck <cohuck@redhat.com>

drivers/s390/cio/ioasm.c

@@ -233,6 +233,7 @@ int hsch(struct subchannel_id schid)
 
 	return ccode;
 }
+EXPORT_SYMBOL(hsch);
 
 static inline int __xsch(struct subchannel_id schid)
 {