ehea: fix use after free

ehea_start_xmit() dereferences skb after its freeing in ehea_xmit3() to
get vlan tags.

Move the offending block before the potential ehea_xmit3() call.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Breno Leitao <leitao@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>