o create a separate tag for each object allocated with bus_dmamem_alloc so
the tag's maxsize is setup appropriately; this reduces memory allocation
for the queue descriptors from 16M to what it should be and also fixes
memory allocation for public key operands
o release bus dma resources on detach so module usage doesn't leak
o remove public key op disable now that bus dma memory allocation is fixed
o collect attach error handling in one place
Sponsored by: Vernier Networks
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