mlxsw: core: Rename mlxsw_afa_qos_cmd to mlxsw_afa_qos_switch_prio_cmd

The original idea was to reuse this set of actions for ECN rewrite as well,
but on second look, it's not such a great idea. These two items should each
have its own command. Rename the existing enum to make it obvious that it
belongs to switch_prio_cmd.

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