mlxsw: spectrum: Track NVE type at FIDs

A follow-up patch will add support for replay and for clearing of
offload marks. These are NVE type-sensitive operations, and to be able
to dispatch them properly, a FID needs to know what NVE type is attached
to it.

Therefore, track the NVE type at struct mlxsw_sp_fid. Extend
mlxsw_sp_fid_vni_set() to take it as an argument, and add
mlxsw_sp_fid_nve_type().

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