SCSI_IOVECTOR remove size field

Remove the size field as it is not used. If we would keep it
we would have to calculate it in scsi_task_set_iov_in/out which
would add unneccassry wals to the iovec array.

Signed-off-by: Peter Lieven <pl@kamp.de>

include/scsi-lowlevel.h

@@ -208,7 +208,6 @@ struct scsi_iovector {
 	struct scsi_iovec *iov;
 	int niov;
 	int nalloc;
-	size_t size;
 	size_t offset;
 	int consumed;
 };