make set_buswide() generic

[br]

Summary

Rename these functions:

bus_dma_dmar_set_buswide()
dmar_is_buswide_ctx()
dmar_set_buswide_ctx()

Not really sure if they are needed for SMMU, but we need to build them on arm64 at least

[br]

Rename bus_dma_dmar_load_ident() as well

[kib]

So please plan for the following two next changes:

1. Removal of headers from iommu.h
2. Providing the vtable for implementation of map/unmap to be used from iommu_gas.

sys/dev/iommu/iommu.h

41

sys/types.h should go first.

43

I think that bringing all that headers into iommu.h was the wrong idea. All of that should be removed and provided by the header' consumers.