The receive ring can strip the C-tag of a frame and report it in the
preheader, but the driver leaves every tag for the stack to pull. Add
NETIF_F_HW_VLAN_CTAG_RX: the ring strips the outer C-tag and the driver
hands it up out of band. A C-tag below an S-tag is not stripped and
stays in the frame.
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Julius Bairaktaris <julius@bairaktaris.de>
Link: https://github.com/openwrt/openwrt/pull/25700
Signed-off-by: Robert Marko <robimarko@gmail.com>