vfio: ccw: define device_api strings

Define vfio-ccw device API strings. CCW vendor driver using mediated
device framework should use this string for device_api attribute.

Reviewed-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Message-Id: <20170317031743.40128-4-bjsdjshi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

include/uapi/linux/vfio.h

@@ -212,6 +212,7 @@ struct vfio_device_info {
 #define VFIO_DEVICE_API_PCI_STRING		"vfio-pci"
 #define VFIO_DEVICE_API_PLATFORM_STRING		"vfio-platform"
 #define VFIO_DEVICE_API_AMBA_STRING		"vfio-amba"
+#define VFIO_DEVICE_API_CCW_STRING		"vfio-ccw"
 
 /**
  * VFIO_DEVICE_GET_REGION_INFO - _IOWR(VFIO_TYPE, VFIO_BASE + 8,