net: cassini: use nested lock annotation

In the cas_lock_tx function we acquire multiple locks in a loop and
need to use nested lock annotation to prevent lockdep warnings.
Reported-by: NMeelis Roos <mroos@linux.ee>
Signed-off-by: NEmil Goode <emilgoode@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/sun/cassini.c

@@ -246,7 +246,7 @@ static inline void cas_lock_tx(struct cas *cp)
 	int i;
 
 	for (i = 0; i < N_TX_RINGS; i++)
-		spin_lock(&cp->tx_lock[i]);
+		spin_lock_nested(&cp->tx_lock[i], i);
 }
 
 static inline void cas_lock_all(struct cas *cp)