r8169: fix the default setting of rx vlan

If the parameter "features" of __rtl8169_set_features() is equal to
dev->features, the variable "changed" is alwayes 0, and nothing would
be changed.

Signed-off-by: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>