bcm63xx_enet: timeout off by one in do_mdio_op()

`while (limit-- >= 0)' reaches -2 after the loop upon timeout.
Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Acked-by: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bcm63xx_enet.c

@@ -90,7 +90,7 @@ static int do_mdio_op(struct bcm_enet_priv *priv, unsigned int data)
 		if (enet_readl(priv, ENET_IR_REG) & ENET_IR_MII)
 			break;
 		udelay(1);
-	} while (limit-- >= 0);
+	} while (limit-- > 0);
 
 	return (limit < 0) ? 1 : 0;
 }