mlxsw: spectrum_qdisc: Track permissible actions per binding

One block can be bound to several qevents. The qevent type that the block
is bound to determines which actions make sense in a given context. In the
particular case of mlxsw, trap cannot be offloaded on a RED mark qevent,
because the trap contract specifies that the packet is dropped in the HW
datapath, and the HW trigger that the action is offloaded to is always
forwarding the packet (in addition to marking in).

Therefore keep track of which actions are permissible at each binding
block. When an attempt is made to bind a certain action at a binding point
where it is not supported, bounce the request.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>