net: dsa: microchip: add the enable_stp_addr pointer in ksz_dev_ops

In order to transmit the STP BPDU packet to the CPU port, the STP
address 01-80-c2-00-00-00 has to be added to static alu table for
ksz8795 series switch. For the ksz9477 switch, there is reserved
multicast table which handles forwarding the particular set of
multicast address to cpu port. So enabling the multicast reserved table
and updated the cpu port index. The stp addr is enabled during the setup
phase using the enable_stp_addr pointer in struct ksz_dev_ops.

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