net: dsa: microchip: Improve phy mode message

Always print the selected phy mode for the CPU port when using the
ksz9477 driver. If the phy mode was changed, also print the previous
mode to aid in debugging.

To make the message more clear, prefix it with the port number which it
applies to and improve the language a little.

Signed-off-by: Paul Barker <pbarker@konsulko.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>