mlxsw: spectrum_fid: Allow setting and clearing NVE properties on FID

In the device, the VNI and the list of remote VTEPs a packet should be
flooded to is a property of the filtering identifier (FID).

During encapsulation, the VNI is taken from the FID the packet was
classified to. During decapsulation, the overlay packet is injected into
a bridge and classified to a FID based on the VNI it came with.

Allow NVE configuration for a FID. Currently, this is only supported
with 802.1D FIDs which are used for VLAN-unaware bridges. However, NVE
configuration is going to be supported with 802.1Q FIDs which is why the
related fields are placed in the common FID struct.

Since the device requires a 1:1 mapping between FID and VNI, the driver
maintains a hashtable keyed by VNI and checks if the VNI is already
associated with an existing 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>