gianfar: disable vlan tag insertion by default

gianfar: disable vlan tag insertion by default

2.6.x kernels require a similar logic change as commit 51b8cbfc
[gianfar: fix bug caused by e1653c3e] introduces for newer kernels.

Gianfar driver originally enables vlan tag insertion by default.
This will lead to unusable connections on some configurations.

Since gianfar nic vlan tag insertion is disabled by default and
it is not enabled any longer, it is not necessary to disable it
again.

Reported-by: Xu Jianrong <roy.xu@huawei.com>
Suggested-by: Wang Feng <sky.wangfeng@huawei.com>
Signed-off-by: Zhu Yanjun <Yanjun.Zhu@windriver.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>