net: dsa: microchip: rename ksz_9477_reg.h to ksz9477_reg.h

Rename ksz_9477_reg.h to ksz9477_reg.h for consistency as the product
name is always KSZ####.

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