mlxsw: spectrum: qdiscs: Create a generic replace function

Create a generic qdisc replace function.
For that goal, add three functions to the qdisc ops struct:
* check_params: Checks if the given parameters are offloadable.
* replace: Offload the given parameters.
* clean_stats: clean the qdisc stats for the offloaded qdisc.
integrate RED offloading into using the new internal replace API.

Signed-off-by: Nogah Frankel <nogahf@mellanox.com>
Reviewed-by: Yuval Mintz <yuvalm@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>