net: dsa: vsc73xx: Add bridge support

net: dsa: vsc73xx: Add bridge support

This patch adds bridge support for the vsc73xx driver.

The vsc73xx requires minimal operations and ithe generic
dsa_tag_8021q_bridge_* API is sufficient.
The forwarding matrix is managed by vsc73xx_port_stp_state_set() ->
vsc73xx_refresh_fwd_map()i routine, which is called immediately after
.port_bridge_join() and .port_bridge_leave().

Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
Link: https://patch.msgid.link/20240713211620.1125910-12-paweldembicki@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>