mlxsw: spectrum: Configure shaper rate and burst size together

In order to allow configuration of burst size together with shaper rate,
extend mlxsw_sp_port_ets_maxrate_set() with a burst_size argument. Convert
call sites to pass 0 (for default).

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