mlxsw: spectrum_router: Split RIF ops array for Spectrum-2 support

Split RIF ops array for Spectrum-1 and Spectrum-2 callbacks in order to
support different sets of operations for loopback RIF handling, as
underlying implementation differs between the ASICs.

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