[SCSI] ibmvfc: Suppress ABTS if target gone

Adds support for a new VIOS feature that allows ibmvfc to
optimize terminate_rport_io by telling the VIOS the target
is no longer accessible on the fabric and that it should
not send an ABTS out on the fabric to the device.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Acked-by: Robert Jennings <rcj@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>