Revert "r8169: improve handling VLAN tag"

This reverts commit 759d0957.

The patch was based on a misunderstanding. As Al Viro pointed out [0]
it's simply wrong on big endian. So let's revert it.

[0] https://marc.info/?t=156200975600004&r=1&w=2



Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>