macvlan: fix panic if lowerdev in a bond

commit a35e2c1b (macvlan: use rx_handler_data pointer to store
macvlan_port pointer V2) added a bug in macvlan_port_create()

Steps to reproduce the bug:

# ifenslave bond0 eth0 eth1

# ip link add link eth0 up name eth0#1 type macvlan
->error EBUSY

# ip link add link eth0 up name eth0#1 type macvlan
->panic


Fix: Dont set IFF_MACVLAN_PORT in error case.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>