can: m_can: use us_to_ktime() where appropriate

The tx_coalesce_usecs_irq are more suitable for using the
us_to_ktime(). This can make the code more concise and
enhance readability.

Signed-off-by: Xichao Zhao <zhao.xichao@vivo.com>
Reviewed-by: Vincent Mailhol <mailhol@kernel.org>
Link: https://patch.msgid.link/20250825090904.248927-1-zhao.xichao@vivo.com
[mkl: remove not needed line break]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

Author: Xichao Zhao

drivers/net/can/m_can/m_can.c

@@ -2213,11 +2213,9 @@ static int m_can_set_coalesce(struct net_device *dev,
 	cdev->tx_coalesce_usecs_irq = ec->tx_coalesce_usecs_irq;
 
 	if (cdev->rx_coalesce_usecs_irq)
-		cdev->irq_timer_wait =
-			ns_to_ktime(cdev->rx_coalesce_usecs_irq * NSEC_PER_USEC);
+		cdev->irq_timer_wait = us_to_ktime(cdev->rx_coalesce_usecs_irq);
 	else
-		cdev->irq_timer_wait =
-			ns_to_ktime(cdev->tx_coalesce_usecs_irq * NSEC_PER_USEC);
+		cdev->irq_timer_wait = us_to_ktime(cdev->tx_coalesce_usecs_irq);
 
 	return 0;
 }