net: mscc: ocelot: make entry_type a member of struct ocelot_multicast

This saves a re-classification of the MDB address on deletion.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>