be2net: fix a Tx stall bug caused by a specific ipv6 packet

The ASIC could lockup in the transmit path when it tries
to insert VLAN in a specific ipv6 packet.
1) Identify the packet which can cause this.
2) Check if the firmware provides a workaround to prevent this.
3) If workaround is not present, drop the packet.
4) If the firmware provides a workaround, insert the VLAN tag in the
packet and inform the firmware to skip further VLAN insertions.

Signed-off-by: Ajit Khaparde <ajit.khaparde@emulex.com>
Signed-off-by: David S. Miller <davem@davemloft.net>