micrel: ksz8851: fixes struct pointer issue

Issue found during code review. This bug has no impact as long as the
ks8851_net structure is the first element of the ks8851_net_spi structure.
As long as the offset to the ks8851_net struct is zero, the container_of()
macro is subtracting 0 and therefore no damage done. But if the
ks8851_net_spi struct is ever modified such that the ks8851_net struct
within it is no longer the first element of the struct, then the bug would
manifest itself and cause problems.

struct ks8851_net is contained within ks8851_net_spi.
ks is contained within kss.
kss is the priv_data of the netdev structure.
Signed-off-by: Jerry Ray <jerry.ray@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/micrel/ks8851_spi.c

@@ -413,7 +413,8 @@ static int ks8851_probe_spi(struct spi_device *spi)
 
 	spi->bits_per_word = 8;
 
-	ks = netdev_priv(netdev);
+	kss = netdev_priv(netdev);
+	ks = &kss->ks8851;
 
 	ks->lock = ks8851_lock_spi;
 	ks->unlock = ks8851_unlock_spi;
@@ -433,8 +434,6 @@ static int ks8851_probe_spi(struct spi_device *spi)
 		 IRQ_RXPSI)	/* RX process stop */
 	ks->rc_ier = STD_IRQ;
 
-	kss = to_ks8851_spi(ks);
-
 	kss->spidev = spi;
 	mutex_init(&kss->lock);
 	INIT_WORK(&kss->tx_work, ks8851_tx_work);