net: dsa: Implement flow_dissect callback for tag_qca

Add flow_dissect for qca tagged packet to get the right hash.

Signed-off-by: Xiaofei Shen <xiaofeis@codeaurora.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>