cxgbe(4): Allow "pass" filters to distribute matching traffic using a
subset of a VI's RSS indirection table.

This makes it possible to make groups out of rx queues and steer
different kinds of traffic to different groups. For example, an
interface with 8 rx queues could have all non-TCP traffic delivered to
queues 0-3 and all TCP traffic to queues 4-7.

Note that it is already possible for filters to steer traffic to a
particular queue or to distribute it using the full indirection table
(much like normal rx does).

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