vlan: dont drop packets from unknown vlans in promiscuous mode

Roger Luethi noticed packets for unknown VLANs getting silently dropped
even in promiscuous mode.

Check for promiscuous mode in __vlan_hwaccel_rx() and vlan_gro_common()
before drops.

As suggested by Patrick, mark such packets to have skb->pkt_type set to
PACKET_OTHERHOST to make sure they are dropped by IP stack.

Reported-by: Roger Luethi <rl@hellgate.ch>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>