mlxsw: spectrum_router: Use RALUE pack helper from abort function

Unify the RALUE register payload packing and use the
__mlxsw_sp_fib_entry_ralue_pack() helper from
__mlxsw_sp_router_set_abort_trap().

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>