net: bridge: Fix missing return assignment from br_vlan_replay_one call

The call to br_vlan_replay_one is returning an error return value but
this is not being assigned to err and the following check on err is
currently always false because err was initialized to zero. Fix this
by assigning err.

Addresses-Coverity: ("'Constant' variable guards dead code")
Fixes: 22f67cdf

 ("net: bridge: add helper to replay VLANs installed on port")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>