This patch adds functions for providing in KSZ9477 switch HSR
(High-availability Seamless Redundancy) hardware offloading.

According to AN3474 application note following features are provided:
- TX packet duplication from host to switch (NETIF_F_HW_HSR_DUP)
- RX packet duplication discarding
- Prevention of packet loop

For last two ones - there is a probability that some packets will not
be filtered in HW (in some special cases - described in AN3474).
Hence, the HSR core code shall be used to discard those not caught frames.

Moreover, some switch registers adjustments are required - like setting
MAC address of HSR network interface.

Additionally, the KSZ9477 switch has been configured to forward frames
between HSR ports (e.g. 1,2) members to provide support for
NETIF_F_HW_HSR_FWD flag.

Join and leave functions are written in a way, that are executed with
single port - i.e. configuration is NOT done only when second HSR port
is configured.
Co-developed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Lukasz Majewski <lukma@denx.de>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>