can: isotp: TX-path: ensure that CAN frame flags are initialized

The previous patch ensures that the TX flags (struct
can_isotp_ll_options::tx_flags) are 0 for classic CAN frames or a user
configured value for CAN-FD frames.

This patch sets the CAN frames flags unconditionally to the ISO-TP TX
flags, so that they are initialized to a proper value. Otherwise when
running "candump -x" on a classical CAN ISO-TP stream shows wrongly
set "B" and "E" flags.

| $ candump any,0:0,#FFFFFFFF -extA
| [...]
| can0  TX B E  713   [8]  2B 0A 0B 0C 0D 0E 0F 00
| can0  TX B E  713   [8]  2C 01 02 03 04 05 06 07
| can0  TX B E  713   [8]  2D 08 09 0A 0B 0C 0D 0E
| can0  TX B E  713   [8]  2E 0F 00 01 02 03 04 05

Fixes: e057dd3fc2 ("can: add ISO 15765-2:2016 transport protocol")
Link: https://lore.kernel.org/r/20210218215434.1708249-2-mkl@pengutronix.de
Cc: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

net/can/isotp.c

@@ -215,8 +215,7 @@ static int isotp_send_fc(struct sock *sk, int ae, u8 flowstatus)
 	if (ae)
 		ncf->data[0] = so->opt.ext_address;
 
-	if (so->ll.mtu == CANFD_MTU)
-		ncf->flags = so->ll.tx_flags;
+	ncf->flags = so->ll.tx_flags;
 
 	can_send_ret = can_send(nskb, 1);
 	if (can_send_ret)
@@ -790,8 +789,7 @@ isotp_tx_burst:
 		so->tx.sn %= 16;
 		so->tx.bs++;
 
-		if (so->ll.mtu == CANFD_MTU)
-			cf->flags = so->ll.tx_flags;
+		cf->flags = so->ll.tx_flags;
 
 		skb->dev = dev;
 		can_skb_set_owner(skb, sk);
@@ -939,8 +937,7 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
 	}
 
 	/* send the first or only CAN frame */
-	if (so->ll.mtu == CANFD_MTU)
-		cf->flags = so->ll.tx_flags;
+	cf->flags = so->ll.tx_flags;
 
 	skb->dev = dev;
 	skb->sk = sk;