net: dsa: microchip: common dsa_switch_ops for ksz switches

At present, ksz8795.c and ksz9477.c have separate dsa_switch_ops
structure initialization. This patch modifies the files such a way that
ksz switches has common dsa_switch_ops in the ksz_common.c file.

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