net: dsa: microchip: move port memory allocation to ksz_common

ksz8795 and ksz9477 init function initializes the memory to dev->ports,
mib counters and assigns the ds real number of ports. Since both the
routines are same, moved the allocation of port memory to
ksz_switch_register after init.

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