The mib counters for the ksz9477 is same for the ksz9477 switch and
LAN937x switch. Hence moving it to ksz_common.c file in order to have it
generic function. The DSA hook get_stats64 now can call ksz_get_stats64.
Signed-off-by: Arun Ramadoss <arun.ramadoss@xxxxxxxxxxxxx>
Reviewed-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>