This commit disables the double tagging recently backported to 19.07.
Operating the switch on the S-Tag had the advantage of being able to
have separate VLANs for the same C-VID on LAN and WAN. However, this
broke the ability to configure C-TAG modifications on the switch. Also
performance took a significant toll.
Fixes: commit 8c191712558c ("ipq40xx: fix ethernet vlan double tagging")
Signed-off-by: David Bauer <mail@david-bauer.net>
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