net: dsa: microchip: ksz8795: change drivers prefix to be generic

The driver can be used on other chips of this type. To reflect
this we rename the drivers prefix from ksz8795 to ksz8.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>