can: flex_can: Correct the checking for frame length in flexcan_start_xmit()

The flexcan_start_xmit() function compares the frame length with data
register length to write frame content into data[0] and data[1]
register. Data register length is 4 bytes and frame maximum length is 8
bytes.

Fix the check that compares frame length with 3. Because the register
length is 4.

Signed-off-by: Luu An Phu <phu.luuan@nxp.com>
Reviewed-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/flexcan.c

@@ -526,7 +526,7 @@ static int flexcan_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		data = be32_to_cpup((__be32 *)&cf->data[0]);
 		flexcan_write(data, &priv->tx_mb->data[0]);
 	}
-	if (cf->can_dlc > 3) {
+	if (cf->can_dlc > 4) {
 		data = be32_to_cpup((__be32 *)&cf->data[4]);
 		flexcan_write(data, &priv->tx_mb->data[1]);
 	}