Cleanup address range checks in ioat(4).

• Deduce allowed address range for bus_dma(9) from the hardware version.

Different versions (CPU generations) have different documented limits.

• Remove difference between address ranges for src/dst and crc. At least

docs for few recent generations of CPUs do not mention anything like that,
while older are already limited with above limits.

• Remove address assertions from arguments. While I do not think the

addresses out of allowed ranges should realistically happen there due to
the platforms physical address limitations, there is now bus_dma(9) to
make sure of that, preferably via IOMMU.

• Since crc now has the same address range as src/dst, remove crc_dmamap,

reusing dst2_dmamap instead.

Discussed with: cem
MFC after: 2 weeks
Sponsored by: iXsystems, Inc.