macvtap: Do not double-count received packets

Currently macvlan will count received packets after calling each
vlans receive handler.   Macvtap attempts to count the packet
yet again when the user reads the packet from the tap socket.
This code doesn't do this consistently either.  Remove the
counting from macvtap and let only macvlan count received
packets.

Signed-off-by: Vlad Yasevich <vyasevic@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>