[qib7322] Use correct length for memset()

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/infiniband/qib7322.c

 		rc = -ENOMEM;
 		goto err_alloc_sendbufavail;
 	}
-	memset ( qib7322->sendbufavail, 0, sizeof ( qib7322->sendbufavail ) );
+	memset ( qib7322->sendbufavail, 0, sizeof ( *qib7322->sendbufavail ) );
 
 	/* Program SendBufAvailAddr into the hardware */
 	memset ( &sendbufavailaddr, 0, sizeof ( sendbufavailaddr ) );