[S390] Add ioctl support for EMC Symmetrix Subsystem Control I/O

EMC Symmetrix Subsystem Control I/O through CKD dasd requires a
specific parameter list sent to the array via a Perform Subsystem
Function CCW. The Symmetrix response is retrieved from the array
via a Read Subsystem Data CCW.

Signed-off-by: Nigel Hislop <hislop_nigel@emc.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>