From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Thu,  1 Feb 2018 11:25:27 +0100

With gcc-4.1.2.:

    net/bridge/br_fdb.c: In function ‘br_fdb_sync_static’:
    net/bridge/br_fdb.c:996: warning: ‘err’ may be used uninitialized in this function

Indeed, if the list is empty, err will be uninitialized, and will be
propagated up as the function return value.

Fix this by preinitializing err to zero.

Fixes: eb7935830d00b9e0 ("net: bridge: use rhashtable for fdbs")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

Applied, thanks Geert.