net: hsr: Properly parse HSRv1 supervisor frames.

While adding support for parsing the redbox supervision frames, the
author added `pull_size' and `total_pull_size' to track the amount of
bytes that were pulled from the skb during while parsing the skb so it
can be reverted/ pushed back at the end.
In the process probably copy&paste error occurred and for the HSRv1 case
the ethhdr was used instead of the hsr_tag. Later the hsr_tag was used
instead of hsr_sup_tag. The later error didn't matter because both
structs have the size so HSRv0 was still working. It broke however HSRv1
parsing because struct ethhdr is larger than struct hsr_tag.

Reinstate the old pulling flow and pull first ethhdr, hsr_tag in v1 case
followed by hsr_sup_tag.

[bigeasy: commit message]

Fixes: eafaa88b ("net: hsr: Add support for redbox supervision frames")'
Suggested-by: Tristram.Ha@microchip.com
Signed-off-by: Lukasz Majewski <lukma@denx.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/hsr/hsr_framereg.c

@@ -288,13 +288,13 @@ void hsr_handle_sup_frame(struct hsr_frame_info *frame)
 
 	/* And leave the HSR tag. */
 	if (ethhdr->h_proto == htons(ETH_P_HSR)) {
-		pull_size = sizeof(struct ethhdr);
+		pull_size = sizeof(struct hsr_tag);
 		skb_pull(skb, pull_size);
 		total_pull_size += pull_size;
 	}
 
 	/* And leave the HSR sup tag. */
-	pull_size = sizeof(struct hsr_tag);
+	pull_size = sizeof(struct hsr_sup_tag);
 	skb_pull(skb, pull_size);
 	total_pull_size += pull_size;