mlxsw: spectrum: Use FID instead of VID when accessing FDB

In the Spectrum ASIC - unlike SwitchX-2 - FDB access is done by
specifying FID as parameter and not VID.

Change the relevant variables and parameters names to reflect that.

Note that this was OK up until now, since FID was always equal to VID,
but with the introduction of VLAN interfaces this is no longer the case.

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