net: dsa: tag_qca: move define to include linux/dsa

Move tag_qca define to include dir linux/dsa as the qca8k require access
to the tagger define to support in-band mdio read/write using ethernet
packet.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>