net: dsa: tag_qca: enable promisc_on_master flag

Ethernet MDIO packets are non-standard and DSA master expects the first
6 octets to be the MAC DA. To address these kind of packet, enable
promisc_on_master flag for the tagger.

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>