Enable card interrupts in our OSM rather than in the core.

Enable card interrupts in our OSM rather than in the core.
This ensures that we don't enter our interrupt handler until
all OSM components it might reference have been fully initialized
during attach.

Remove vestiges of untagged queue handling.

Add hints to ahd_get_scb() so it knows what type of SCB collision
management to perform for each new transaction.

Properly disable/enable IU_REQ with changes in tagged queuing and
disconnection settings passed in by CAM.