Partially revert change made in r212061. r212061 relied on bus_dma(9)'s capability which honors boundary restrictions of DMA tag for dynamic buffers. However it seems this does not work well and it triggered watchodg timeouts on controller that has the hardware bug. It's not clear whether there is still another hardware bug not mentioned in errata. This should be revisited since this change shall make use of bounce buffers which in turn reduces performance a lot on systems that have more than 4GB memory.
Partially revert change made in r212061. r212061 relied on
bus_dma(9)'s capability which honors boundary restrictions of DMA
tag for dynamic buffers. However it seems this does not work well
and it triggered watchodg timeouts on controller that has the
hardware bug. It's not clear whether there is still another
hardware bug not mentioned in errata. This should be revisited
since this change shall make use of bounce buffers which in turn
reduces performance a lot on systems that have more than 4GB
memory.

Reported by:	Michael L. Squires (mikes <> siralan dot org)
Tested by:	Michael L. Squires (mikes <> siralan dot org)
MFC after:	3 days

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase