mlxsw: spectrum: Rename IPIP-related netdevice handlers

To distinguish between events related to tunnel device itself and its
bound device, rename a number of functions related to handling tunneling
netdevice events to include _ol_ (for "overlay") in the name. That
leaves room in the namespace for underlay-related functions, which would
have _ul_ in the name.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>