mlxsw: spectrum: Change mlxsw_sp_rif_vlan_fid_op() to be dedicated for FID RIFs

The function was designed to configure both VLAN and FID RIFs, but
currently the driver does not use VLAN RIFs. Instead, it emulates VLAN
RIFs using FID RIFs.

As part of the conversion to the unified bridge model, the driver will
need to use VLAN RIFs, but they will be configured differently from FID
RIFs.

As a preparation for this change, rename the function to reflect the
fact that it is specific to FID RIFs and do not pass the RIF type as an
argument.

This leaves mlxsw_reg_ritr_fid_set() unused, so remove it.

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>