net: dsa: microchip: Move ksz_cfg and ksz_port_cfg to ksz9477.c

These functions are only used by the KSZ9477 code, move them from
the header into that code. Note that these functions will be soon
replaced by regmap equivalents.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Tristram Ha <Tristram.Ha@microchip.com>
Cc: Woojung Huh <Woojung.Huh@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>