iscsi: drop unused IscsiAIOCB.qiov field

The IscsiAIOCB.qiov field has been unused since commit
063c3378 ("block/iscsi: introduce
bdrv_co_{readv, writev, flush_to_disk}") back in 2013.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20170327165005.22038-1-stefanha@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

block/iscsi.c

@@ -103,7 +103,6 @@ typedef struct IscsiTask {
 
 typedef struct IscsiAIOCB {
     BlockAIOCB common;
-    QEMUIOVector *qiov;
     QEMUBH *bh;
     IscsiLun *iscsilun;
     struct scsi_task *task;