mlxsw: spectrum_fid: Clear NVE configuration when destroying 802.1D FIDs

802.1D FIDs are used to represent VLAN-unaware bridges and currently
this is the only type of FID that supports NVE configuration.

Since the NVE tunnel device does not take a reference on the FID, it is
possible for the FID to be destroyed when it still has NVE
configuration.

Therefore, when destroying the FID make sure to disable its NVE
configuration.

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