net: txgbe: fix to control VLAN strip

When VLAN tag strip is changed to enable or disable, the hardware requires
the Rx ring to be in a disabled state, otherwise the feature cannot be
changed.

Fixes: f3b03c65 ("net: wangxun: Implement vlan add and kill functions")
Signed-off-by: Jiawen Wu <jiawenwu@trustnetic.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>