o Move iommu_test_boundary() to sys/iommu.h
o Rename DMAR -> IOMMU in comments
o Add IOMMU_PAGE_SIZE / IOMMU_PAGE_MASK macroses
o x86 only: dmar_quirks_pre_use() / dmar_instantiate_rmrr_ctxs()

Reviewed by: kib
Sponsored by: DARPA/AFRL
Differential Revision: https://reviews.freebsd.org/D25665