[S390] cio: Introduce subchannel->private.

Introduce a private pointer in struct subchannel to store
per-subchannel type data (cannot use dev->priv since this
is already used for something else).

Create a new header io_sch.h for I/O subchannel specific structures
and instructions.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/cio/device.h b/drivers/s390/cio/device.h
index 6183731..87576fe 100644
--- a/drivers/s390/cio/device.h
+++ b/drivers/s390/cio/device.h
@@ -5,6 +5,8 @@
 #include <asm/atomic.h>
 #include <linux/wait.h>
 
+#include "io_sch.h"
+
 /*
  * states of the device statemachine
  */