net: dsa: microchip: ksz8795: use common xmii function

This patch updates the ksz8795 cpu configuration to use the ksz common
xmii set functions.

Signed-off-by: Arun Ramadoss <arun.ramadoss@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>