net: mana: Add handling of CQE_RX_TRUNCATED

The proper way to drop this kind of CQE is advancing rxq tail
without indicating the packet to the upper network layer.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>