From: <sean.wang@mediatek.com>
Date: Sat, 22 Jul 2017 20:45:55 +0800

From: Sean Wang <sean.wang@mediatek.com>

Potential dangerous invalid memory might be accessed if invalid mac value
reflected from the forward port field in rxd4 caused by possible potential
hardware defects. So added a simple sanity checker to avoid the kind of
situation happening.

Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Acked-by: John Crispin <john@phrozen.org>

Applied.