net: dsa: microchip: move ksz_dev_ops to ksz_common.c

This patch move the ksz_dev_ops from individual files to ksz_common.c.
And the dev_ops is assigned to ksz_device based on the switch detect.
This reduces the redundant function and allows to reuse the
functionality for LAN937x which has similar register set.

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