lantiq: net: fix duplicated skb in rx descriptor ring

lantiq: net: fix duplicated skb in rx descriptor ring

[ Upstream commit 7ea6cd16f1599c1eac6018751eadbc5fc736b99a ]

The previous commit didn't fix the bug properly. By mistake, it replaces
the pointer of the next skb in the descriptor ring instead of the current
one. As a result, the two descriptors are assigned the same SKB. The error
is seen during the iperf test when skb_put tries to insert a second packet
and exceeds the available buffer.

Fixes: c7718ee96dbc ("net: lantiq: fix memory corruption in RX ring ")
Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>