[S390] cio: Add chsc subchannel driver.

This patch adds a driver for subchannels of type chsc.

A device /dev/chsc is created which may be used to issue ioctls to:
- obtain information about the machine's I/O configuration
- dynamically change the machine's I/O configuration via
  asynchronous chsc commands

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/include/asm-s390/isc.h b/include/asm-s390/isc.h
index fe56f7b..34bb891 100644
--- a/include/asm-s390/isc.h
+++ b/include/asm-s390/isc.h
@@ -14,6 +14,7 @@
 /* Regular I/O interrupts. */
 #define IO_SCH_ISC 3			/* regular I/O subchannels */
 #define CONSOLE_ISC 1			/* console I/O subchannel */
+#define CHSC_SCH_ISC 7			/* CHSC subchannels */
 /* Adapter interrupts. */
 #define QDIO_AIRQ_ISC IO_SCH_ISC	/* I/O subchannel in qdio mode */