Add support for flushing the MAC table on a given port in the ocelot
switch library, and use this functionality in the felix DSA driver.

This operation is needed when a port leaves a bridge to become
standalone, and when the learning is disabled, and when the STP state
changes to a state where no FDB entry should be present.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20220107144229.244584-1-vladimir.oltean@nxp.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>