net: mscc: ocelot: rename ocelot_netdevice_port_event to ocelot_netdevice_changeupper

ocelot_netdevice_port_event treats a single event, NETDEV_CHANGEUPPER.
So we can remove the check for the type of event, and rename the
function to be more suggestive, since there already is a function with a
very similar name of ocelot_netdevice_event.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>