net: dsa: microchip: ksz8795: move variable assignments from detect to init

This patch moves all variable assignments to the init function. It
leaves the detect function for its single purpose to detect which chip
version is found.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>