net: dsa: microchip: add regmap_range for KSZ9477 chip

Add register validation for KSZ9477

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>