mlxsw: reg: Extend FDB flush types for NVE

The device has the ability to flush all the FDB records that perform NVE
encapsulation or only a subset of these with a specific filtering
identifier (FID).

Expose these types so that they could be used by subsequent patches
where we need to flush the FDB records when an NVE device is unlinked
from a bridge (FID).

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