net: dsa: mv88e6xxx: Move devlink code into its own file

There will soon be more devlink code. Move the existing code into a
file of its own, before we start adding this new code.

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
4 files changed