can: janz-ican3: add software tx timestamp

TX timestamps were added to the can_put_echo_skb() function of can_dev
modules in [1]. However, janz-ican3 does not rely on that function but
instead implements its own echo_skb logic. As such it does not offer
TX timestamping.

Add a call to skb_tx_timestamp() in the ican3_put_echo_skb() function
so that the module now supports TX software timestamps.

[1] commit 741b91f ("can: dev: can_put_echo_skb(): add software
tx timestamps")
Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=741b91f1b0ea34f00f6a7d4539b767c409291fcf

Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://lore.kernel.org/all/20220727101641.198847-3-mailhol.vincent@wanadoo.fr
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/janz-ican3.c

@@ -1277,6 +1277,8 @@ static void ican3_put_echo_skb(struct ican3_dev *mod, struct sk_buff *skb)
 	if (!skb)
 		return;
 
+	skb_tx_timestamp(skb);
+
 	/* save this skb for tx interrupt echo handling */
 	skb_queue_tail(&mod->echoq, skb);
 }