vfio-ccw: add handling for async channel instructions

Add a region to the vfio-ccw device that can be used to submit
asynchronous I/O instructions. ssch continues to be handled by the
existing I/O region; the new region handles hsch and csch.

Interrupt status continues to be reported through the same channels
as for ssch.

Acked-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Farhan Ali <alifm@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

include/uapi/linux/vfio.h

@@ -354,6 +354,8 @@ struct vfio_region_gfx_edid {
 };
 
 #define VFIO_REGION_TYPE_CCW			(2)
+/* ccw sub-types */
+#define VFIO_REGION_SUBTYPE_CCW_ASYNC_CMD	(1)
 
 /*
  * 10de vendor sub-type