- We don't need to fall back to uncacheable memory to satisfy BUS_DMA_COHERENT
requests on these CPUs.
- The bus_dmamap_sync() is a no-op for these CPUs.
A side-effect of this change is rename DMAMAP_COHERENT flag to
DMAMAP_UNCACHEABLE. This conveys the purpose of the flag more accurately.
Reviewed by: gonzo, imp