mlxsw: spectrum_matchall: Publish matchall data structures

A following patch introduces offloading of filters attached to blocks bound
to the RED tail_drop qevent. The only classifier that mlxsw will permit in
this role is matchall. mlxsw currently offloads matchall filters used with
clsact qdisc. The data structures used for that offload will come handy for
the qevent offload as well. Publish them in spectrum.h.

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