net: dsa: microchip: move setup function to ksz_common

This patch move the common initialization of switches to ksz_setup and
perform the switch specific initialization using the ksz_dev_ops
function pointer.

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