This re-enables offloading features disabled by
commit 9da2b56760 ("ipq40xx: fix ethernet vlan double tagging").
Single-PHY devices use port-based VLANs on the switch, therefore no
S-TAG magic is involved here. Re-enabling these features restores
throughput back to 950 Mbit/s.
Reported-by: Jannis Pinter <jannis@pinterjann.is>
Signed-off-by: David Bauer <mail@david-bauer.net>