Revert "net: maintain namespace isolation between vlan and real device"

Revert "net: maintain namespace isolation between vlan and real device"

This reverts commit be5d73addae14db55f25596e61b044d30f097425.

It causes regressions for S390 devices, because it does an
unconditional DST drop on SKBs for vlans and the QETH device
needs the neighbour entry hung off the DST for certain things
on transmit.

Arnd can't remember exactly why he even needed this change.

Conflicts:

	drivers/net/macvlan.c
	net/8021q/vlan_dev.c
	net/core/dev.c

Signed-off-by: David S. Miller <davem@davemloft.net>