can: gs_usb: gs_can_start_xmit(): zero-initialize hf->{flags,reserved}

No information is deliberately sent in hf->flags in host -> device
communications, but the open-source candleLight firmware echoes it
back, which can result in the GS_CAN_FLAG_OVERFLOW flag being set and
generating spurious ERRORFRAMEs.

While there also initialize the reserved member with 0.

Fixes: d08e973 ("can: gs_usb: Added support for the GS_USB CAN devices")
Link: https://lore.kernel.org/all/20220106002952.25883-1-brian.silverman@bluerivertech.com
Link: candle-usb/candleLight_fw#87
Cc: stable@vger.kernel.org
Signed-off-by: Brian Silverman <brian.silverman@bluerivertech.com>
[mkl: initialize the reserved member, too]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

Author: brian-brt

drivers/net/can/usb/gs_usb.c

@@ -508,6 +508,8 @@ static netdev_tx_t gs_can_start_xmit(struct sk_buff *skb,
 
 	hf->echo_id = idx;
 	hf->channel = dev->channel;
+	hf->flags = 0;
+	hf->reserved = 0;
 
 	cf = (struct can_frame *)skb->data;