Fix rx_len_adj to avoid leaking the ethernet FCS into the actual frame
data in single line mode (the default)
Fixes: https://github.com/openwrt/openwrt/issues/20983
Signed-off-by: Markus Petri <devel@isjunk.org>
Link: https://github.com/openwrt/openwrt/pull/21045
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
(cherry picked from commit 487178f8b003bf2e06b9f989b46f8b5c36181910)
(cherry picked from commit d9c5716d1d75e652d57b42a514b20145a24eee18)