via-velocity: don't oops on MTU change (resend)

The VIA veloicty driver needs the following to allow changing MTU when down.
The buffer size needs to be computed when device is brought up, not when
device is initialized.  This also fixes a bug where the buffer size was
computed differently on change_mtu versus initial setting.
Signed-off-by: NStephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: NJeff Garzik <jeff@garzik.org>

drivers/net/via-velocity.c

@@ -1242,6 +1242,9 @@ static int velocity_rx_refill(struct velocity_info *vptr)
 static int velocity_init_rd_ring(struct velocity_info *vptr)
 {
 	int ret;
+	int mtu = vptr->dev->mtu;
+
+	vptr->rx_buf_sz = (mtu <= ETH_DATA_LEN) ? PKT_BUF_SZ : mtu + 32;
 
 	vptr->rd_info = kcalloc(vptr->options.numrx,
 				sizeof(struct velocity_rd_info), GFP_KERNEL);
@@ -1898,8 +1901,6 @@ static int velocity_open(struct net_device *dev)
 	struct velocity_info *vptr = netdev_priv(dev);
 	int ret;
 
-	vptr->rx_buf_sz = (dev->mtu <= 1504 ? PKT_BUF_SZ : dev->mtu + 32);
-
 	ret = velocity_init_rings(vptr);
 	if (ret < 0)
 		goto out;
@@ -1978,12 +1979,6 @@ static int velocity_change_mtu(struct net_device *dev, int new_mtu)
 		velocity_free_rd_ring(vptr);
 
 		dev->mtu = new_mtu;
-		if (new_mtu > 8192)
-			vptr->rx_buf_sz = 9 * 1024;
-		else if (new_mtu > 4096)
-			vptr->rx_buf_sz = 8192;
-		else
-			vptr->rx_buf_sz = 4 * 1024;
 
 		ret = velocity_init_rd_ring(vptr);
 		if (ret < 0)