can: at91_can: fix compiler warning in at91_irq_err_state

This patch fixes the following compiler warning:

drivers/net/can/at91_can.c: In function 'at91_irq_err_state':
drivers/net/can/at91_can.c:779: warning: 'reg_ier' may be used uninitialized in this function
drivers/net/can/at91_can.c:779: warning: 'reg_idr' may be used uninitialized in this function
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/can/at91_can.c

@@ -764,7 +764,7 @@ static void at91_irq_err_state(struct net_device *dev,
 		struct can_frame *cf, enum can_state new_state)
 {
 	struct at91_priv *priv = netdev_priv(dev);
-	u32 reg_idr, reg_ier, reg_ecr;
+	u32 reg_idr = 0, reg_ier = 0, reg_ecr;
 	u8 tec, rec;
 
 	reg_ecr = at91_read(priv, AT91_ECR);