can: m_can: Use u32 for putidx

putidx is not an integer normally, it is an unsigned field used in
hardware registers. Use a u32 for it.
Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/all/20240207093220.2681425-9-msp@baylibre.comSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/m_can/m_can.c

@@ -486,7 +486,7 @@ static void m_can_clean(struct net_device *net)
 	struct m_can_classdev *cdev = netdev_priv(net);
 
 	if (cdev->tx_skb) {
-		int putidx = 0;
+		u32 putidx = 0;
 
 		net->stats.tx_errors++;
 		if (cdev->version > 30)
@@ -1695,12 +1695,12 @@ static int m_can_close(struct net_device *dev)
 	return 0;
 }
 
-static int m_can_next_echo_skb_occupied(struct net_device *dev, int putidx)
+static int m_can_next_echo_skb_occupied(struct net_device *dev, u32 putidx)
 {
 	struct m_can_classdev *cdev = netdev_priv(dev);
 	/*get wrap around for loopback skb index */
 	unsigned int wrap = cdev->can.echo_skb_max;
-	int next_idx;
+	u32 next_idx;
 
 	/* calculate next index */
 	next_idx = (++putidx >= wrap ? 0 : putidx);
@@ -1719,7 +1719,7 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
 	u32 cccr, fdflags;
 	u32 txfqs;
 	int err;
-	int putidx;
+	u32 putidx;
 
 	cdev->tx_skb = NULL;