can: isotp: change error format from decimal to symbolic error names

This patch changes the format string for errors from decimal %d to
symbolic error names %pe to achieve more comprehensive log messages.

Link: https://lore.kernel.org/r/20210427052150.2308-2-menschel.p@posteo.de
Signed-off-by: Patrick Menschel <menschel.p@posteo.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

net/can/isotp.c

@@ -221,8 +221,8 @@ static int isotp_send_fc(struct sock *sk, int ae, u8 flowstatus)
 
 	can_send_ret = can_send(nskb, 1);
 	if (can_send_ret)
-		pr_notice_once("can-isotp: %s: can_send_ret %d\n",
-			       __func__, can_send_ret);
+		pr_notice_once("can-isotp: %s: can_send_ret %pe\n",
+			       __func__, ERR_PTR(can_send_ret));
 
 	dev_put(dev);
 
@@ -798,8 +798,8 @@ static enum hrtimer_restart isotp_tx_timer_handler(struct hrtimer *hrtimer)
 
 		can_send_ret = can_send(skb, 1);
 		if (can_send_ret)
-			pr_notice_once("can-isotp: %s: can_send_ret %d\n",
-				       __func__, can_send_ret);
+			pr_notice_once("can-isotp: %s: can_send_ret %pe\n",
+				       __func__, ERR_PTR(can_send_ret));
 
 		if (so->tx.idx >= so->tx.len) {
 			/* we are done */
@@ -946,8 +946,8 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
 	err = can_send(skb, 1);
 	dev_put(dev);
 	if (err) {
-		pr_notice_once("can-isotp: %s: can_send_ret %d\n",
-			       __func__, err);
+		pr_notice_once("can-isotp: %s: can_send_ret %pe\n",
+			       __func__, ERR_PTR(err));
 		return err;
 	}