net: dsa: mv88e6xxx: Use EDSA on mv88e6097

Use DSA_TAG_PROTO_EDSA as tag_protocol for the mv88e6097. The
initialisation was missing before.

Fixes: a1f482aa8c33 ("net: dsa: mv88e6xxx: Move the tagging protocol into info")
Signed-off-by: Stefan Eichenberger <stefan.eichenberger@netmodule.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>